`c3_pln_stv.metta` test crashes on Rust borrow checker.

[stustd]

Describe the bug
Crashed on Rust borrow checker, in
branch main, commit id f26ee88

To Reproduce
Running script:
RUST_LOG=hyperon=debug metta-py tests/scripts/c3_pln_stv.metta

Expected behavior
Expected some result.

Actual behavior
Crashed on Rust borrow checker, with

...
[2025-05-13T15:07:19Z DEBUG hyperon::metta::runner::modules] import_all_from_dependency: importing from top:corelib into top:catalog
[2025-05-13T15:07:19Z DEBUG hyperon::metta::runner::modules] import_all_from_dependency: importing from top:stdlib into top:catalog
[2025-05-13T15:07:19Z DEBUG hyperon::metta::runner::modules] import_all_from_dependency: importing from top:corelib into top
[2025-05-13T15:07:19Z DEBUG hyperon::metta::runner::modules] import_all_from_dependency: importing from top:stdlib into top
[2025-05-13T15:07:19Z DEBUG hyperon::space::grounding] GroundingSpace::add: GroundingSpace-top, atom: (= (min $a $b) (if (< $a $b) $a $b))
[2025-05-13T15:07:19Z DEBUG hyperon::space::grounding] GroundingSpace::add: GroundingSpace-top, atom: (= (s-tv (stv $s $c)) $s)
[2025-05-13T15:07:19Z DEBUG hyperon::space::grounding] GroundingSpace::add: GroundingSpace-top, atom: (= (c-tv (stv $s $c)) $c)

thread '<unnamed>' panicked at lib/src/space/mod.rs:314:34:
already mutably borrowed: BorrowError
note: run with `RUST_BACKTRACE=1` environment variable to display a backtrace

thread '<unnamed>' panicked at library/core/src/panicking.rs:218:5:
panic in a function that cannot unwind
stack backtrace:
   0:     0x7f289d4fbf62 - std::backtrace_rs::backtrace::libunwind::trace::ha1616cdbc2eab182
                               at /rustc/092a284ba0421695f2032c947765429fd7095796/library/std/src/../../backtrace/src/backtrace/libunwind.rs:117:9
   1:     0x7f289d4fbf62 - std::backtrace_rs::backtrace::trace_unsynchronized::hf9b2cd84fd49ce4e
                               at /rustc/092a284ba0421695f2032c947765429fd7095796/library/std/src/../../backtrace/src/backtrace/mod.rs:66:14
   2:     0x7f289d4fbf62 - std::sys::backtrace::_print_fmt::h3feb7011183def60
                               at /rustc/092a284ba0421695f2032c947765429fd7095796/library/std/src/sys/backtrace.rs:66:9
   3:     0x7f289d4fbf62 - <std::sys::backtrace::BacktraceLock::print::DisplayBacktrace as core::fmt::Display>::fmt::hdddccddb549971e5
                               at /rustc/092a284ba0421695f2032c947765429fd7095796/library/std/src/sys/backtrace.rs:39:26
   4:     0x7f289d5494e3 - core::fmt::rt::Argument::fmt::h2ad0c13cab3c9140
                               at /rustc/092a284ba0421695f2032c947765429fd7095796/library/core/src/fmt/rt.rs:153:76
   5:     0x7f289d5494e3 - core::fmt::write::h941840204efeeab2
                               at /rustc/092a284ba0421695f2032c947765429fd7095796/library/core/src/fmt/mod.rs:1481:21
   6:     0x7f289d4f0b73 - std::io::default_write_fmt::hd0badb82c1b154af
                               at /rustc/092a284ba0421695f2032c947765429fd7095796/library/std/src/io/mod.rs:639:11
   7:     0x7f289d4f0b73 - std::io::Write::write_fmt::h1ecac89a1b25143e
                               at /rustc/092a284ba0421695f2032c947765429fd7095796/library/std/src/io/mod.rs:1914:13
   8:     0x7f289d4fbdb2 - std::sys::backtrace::BacktraceLock::print::ha43886285fe1612d
                               at /rustc/092a284ba0421695f2032c947765429fd7095796/library/std/src/sys/backtrace.rs:42:9
   9:     0x7f289d4ff8ac - std::panicking::default_hook::{{closure}}::h5aa9fc3e128ac2ad
                               at /rustc/092a284ba0421695f2032c947765429fd7095796/library/std/src/panicking.rs:300:22
  10:     0x7f289d4ff6af - std::panicking::default_hook::he5473a82f6a1d174
                               at /rustc/092a284ba0421695f2032c947765429fd7095796/library/std/src/panicking.rs:327:9
  11:     0x7f289d5002c2 - std::panicking::rust_panic_with_hook::h56eacc1263fc7395
                               at /rustc/092a284ba0421695f2032c947765429fd7095796/library/std/src/panicking.rs:833:13
  12:     0x7f289d500036 - std::panicking::begin_panic_handler::{{closure}}::h24d26231c2beb50b
                               at /rustc/092a284ba0421695f2032c947765429fd7095796/library/std/src/panicking.rs:699:13
  13:     0x7f289d4fc469 - std::sys::backtrace::__rust_end_short_backtrace::ha0d3e85268487187
                               at /rustc/092a284ba0421695f2032c947765429fd7095796/library/std/src/sys/backtrace.rs:168:18
  14:     0x7f289d4ffcfd - __rustc[b63dcf0b63ea116e]::rust_begin_unwind
                               at /rustc/092a284ba0421695f2032c947765429fd7095796/library/std/src/panicking.rs:697:5
  15:     0x7f289cbd76dd - core::panicking::panic_nounwind_fmt::runtime::h6757a50ad98bb1b8
                               at /rustc/092a284ba0421695f2032c947765429fd7095796/library/core/src/panicking.rs:117:22
  16:     0x7f289cbd76dd - core::panicking::panic_nounwind_fmt::h5ff8332cc776c8a6
                               at /rustc/092a284ba0421695f2032c947765429fd7095796/library/core/src/intrinsics/mod.rs:3193:9
  17:     0x7f289cbd7772 - core::panicking::panic_nounwind::hb5b44e4f5dcdaee2
                               at /rustc/092a284ba0421695f2032c947765429fd7095796/library/core/src/panicking.rs:218:5
  18:     0x7f289cbd7932 - core::panicking::panic_cannot_unwind::hcc6731bc396b9893
                               at /rustc/092a284ba0421695f2032c947765429fd7095796/library/core/src/panicking.rs:323:5
  19:     0x7f289cc8fbd9 - metta_run
                               at /home/hjansen/workspace/Actryx/projects/internal/AxCog/subprojects/opencog-hyperon/hyperon-experimental/c/src/metta.rs:993:1
  20:     0x7f289cc0752c - _ZZL23pybind11_init_hyperonpyRN8pybind117module_EENK5$_118clER7CStructI7metta_tER12CSExprParser
                               at /home/hjansen/workspace/Actryx/projects/internal/AxCog/subprojects/opencog-hyperon/hyperon-experimental/python/hyperonpy.cpp:1098:13
  21:     0x7f289cc07499 - _ZNO8pybind116detail15argument_loaderIJR7CStructI7metta_tER12CSExprParserEE9call_implINS_4listERZL23pybind11_init_hyperonpyRNS_7module_EE5$_118JLm0ELm1EENS0_9void_typeEEET_OT0_NS0_14index_sequenceIJXspT1_EEEEOT2_
                               at /home/hjansen/.conan2/p/pybin45ada33f9a625/p/include/pybind11/detail/../cast.h:1439:16
  22:     0x7f289cc0741c - _ZNO8pybind116detail15argument_loaderIJR7CStructI7metta_tER12CSExprParserEE4callINS_4listENS0_9void_typeERZL23pybind11_init_hyperonpyRNS_7module_EE5$_118EENSt9enable_ifIXntsr7is_voidIT_EE5valueESH_E4typeEOT1_
                               at /home/hjansen/.conan2/p/pybin45ada33f9a625/p/include/pybind11/detail/../cast.h:1407:42
  23:     0x7f289cc0735b - _ZZN8pybind1112cpp_function10initializeIZL23pybind11_init_hyperonpyRNS_7module_EE5$_118NS_4listEJR7CStructI7metta_tER12CSExprParserEJNS_4nameENS_5scopeENS_7siblingEA34_cEEEvOT_PFT0_DpT1_EDpRKT2_ENKUlRNS_6detail13function_callEE_clEST_
                               at /home/hjansen/.conan2/p/pybin45ada33f9a625/p/include/pybind11/pybind11.h:249:69
  24:     0x7f289cc072b9 - _ZZN8pybind1112cpp_function10initializeIZL23pybind11_init_hyperonpyRNS_7module_EE5$_118NS_4listEJR7CStructI7metta_tER12CSExprParserEJNS_4nameENS_5scopeENS_7siblingEA34_cEEEvOT_PFT0_DpT1_EDpRKT2_ENUlRNS_6detail13function_callEE_8__invokeEST_
                               at /home/hjansen/.conan2/p/pybin45ada33f9a625/p/include/pybind11/pybind11.h:224:21
  25:     0x7f289cc213f3 - _ZN8pybind1112cpp_function10dispatcherEP7_objectS2_S2_
                               at /home/hjansen/.conan2/p/pybin45ada33f9a625/p/include/pybind11/pybind11.h:929:30
  26:     0x7f289eb9d5c2 - cfunction_call
  27:     0x7f289ebed387 - _PyEval_EvalFrameDefault
  28:     0x7f289ed16e78 - PyEval_EvalCode
  29:     0x7f289ed52f6a - run_mod.llvm.14556718170306304843
  30:     0x7f289ea99c3f - pyrun_file
  31:     0x7f289ea991b8 - _PyRun_SimpleFileObject
  32:     0x7f289ea98e2a - _PyRun_AnyFileObject
  33:     0x7f289eaa442e - pymain_run_file_obj
  34:     0x7f289eaa41e4 - pymain_run_file
  35:     0x7f289ed6c069 - Py_RunMain
  36:     0x7f289ed6c67f - pymain_main
  37:     0x7f289ed6c73c - Py_BytesMain
  38:     0x7f289e42a1ca - __libc_start_call_main
                               at ./csu/../sysdeps/nptl/libc_start_call_main.h:58:16
  39:     0x7f289e42a28b - __libc_start_main_impl
                               at ./csu/../csu/libc-start.c:360:3
  40:           0x6000a9 - _start
  41:                0x0 - <unknown>
thread caused non-unwinding panic. aborting.
Aborted (core dumped)

Additional context
NA