Fix compilation with HAVE_MPI

[antonvnv]

[ 35%] Building CXX object src/CMakeFiles/mmseqs-framework.dir/util/results2msa.cpp.o
/home/avorontsov/s/rna/MMseqs2/src/util/results2msa.cpp: In function ‘int results2msa(int, const char**, const Command&)’:
/home/avorontsov/s/rna/MMseqs2/src/util/results2msa.cpp:146:22: error: request for member ‘decomposeDomainByAminoAcid’ in ‘resultReaders.std::vector<DBReader<unsigned int>*>::operator[](0)’, which is of pointer type ‘__gnu_cxx::__alloc_traits<std::allocator<DBReader<unsigned int>*>, DBReader<unsigned int>*>::value_type’ {aka ‘DBReader<unsigned int>*’} (maybe you meant to use ‘->’ ?)
  146 |     resultReaders[0].decomposeDomainByAminoAcid(MMseqsMPI::rank, MMseqsMPI::numProc, &dbFrom, &dbSize);
      |                      ^~~~~~~~~~~~~~~~~~~~~~~~~~
make[2]: *** [src/CMakeFiles/mmseqs-framework.dir/build.make:1927: src/CMakeFiles/mmseqs-framework.dir/util/results2msa.cpp.o] Error 1
make[1]: *** [CMakeFiles/Makefile2:1083: src/CMakeFiles/mmseqs-framework.dir/all] Error 2
make: *** [Makefile:136: all] Error 2

[ 36%] Building CXX object src/CMakeFiles/mmseqs-framework.dir/util/results2profile.cpp.o
/home/avorontsov/s/rna/MMseqs2/src/util/results2profile.cpp: In function ‘int results2profile(int, const char**, const Command&, bool)’:
/home/avorontsov/s/rna/MMseqs2/src/util/results2profile.cpp:75:19: error: request for member ‘decomposeDomainByAminoAcid’ in ‘resultDbrs.std::vector<DBReader<unsigned int>*>::operator[](0)’, which is of pointer ty
pe ‘__gnu_cxx::__alloc_traits<std::allocator<DBReader<unsigned int>*>, DBReader<unsigned int>*>::value_type’ {aka ‘DBReader<unsigned int>*’} (maybe you meant to use ‘->’ ?)
   75 |     resultDbrs[0].decomposeDomainByAminoAcid(MMseqsMPI::rank, MMseqsMPI::numProc, &dbFrom, &dbSize);
      |                   ^~~~~~~~~~~~~~~~~~~~~~~~~~
make[2]: *** [src/CMakeFiles/mmseqs-framework.dir/build.make:1969: src/CMakeFiles/mmseqs-framework.dir/util/results2profile.cpp.o] Error 1
make[1]: *** [CMakeFiles/Makefile2:1083: src/CMakeFiles/mmseqs-framework.dir/all] Error 2
make: *** [Makefile:136: all] Error 2