ERROR: ArgumentError: cannot convert NULL to string

[cacilhas]

julia> docs = [doc for doc in find(foo, query("x"=>3))]
1-element Array{LibBSON.BSONObject,1}:
Error showing value of type Array{LibBSON.BSONObject,1}:
ERROR: ArgumentError: cannot convert NULL to string
in unsafe_string at ./strings/basic.jl:56 [inlined]
in convert(::Type{AbstractString}, ::LibBSON.BSONObject) at /Users/cacilhas/.julia/v0.5/LibBSON/src/BSONObject.jl:74
in show(::IOContext{Base.AbstractIOBuffer{Array{UInt8,1}}}, ::LibBSON.BSONObject) at /Users/cacilhas/.julia/v0.5/LibBSON/src/BSONObject.jl:86
in #sprint#316(::IOContext{Base.Terminals.TTYTerminal}, ::Function, ::Int64, ::Function, ::LibBSON.BSONObject, ::Vararg{LibBSON.BSONObject,N}) at ./strings/io.jl:35
in (::Base.#kw##sprint)(::Array{Any,1}, ::Base.#sprint, ::Int64, ::Function, ::LibBSON.BSONObject, ::Vararg{LibBSON.BSONObject,N}) at ./:0
in alignment(::IOContext{Base.Terminals.TTYTerminal}, ::Array{LibBSON.BSONObject,1}, ::Array{Int64,1}, ::Array{Int64,1}, ::Int64, ::Int64, ::Int64) at ./show.jl:1278
in print_matrix(::IOContext{Base.Terminals.TTYTerminal}, ::Array{LibBSON.BSONObject,1}, ::String, ::String, ::String, ::String, ::String, ::String, ::Int64, ::Int64) at ./show.jl:1407
in print_matrix(::IOContext{Base.Terminals.TTYTerminal}, ::Array{LibBSON.BSONObject,1}, ::String, ::String, ::String) at ./show.jl:1379
in #showarray#342(::Bool, ::Function, ::IOContext{Base.Terminals.TTYTerminal}, ::Array{LibBSON.BSONObject,1}, ::Bool) at ./show.jl:1618
in display(::Base.REPL.REPLDisplay{Base.REPL.LineEditREPL}, ::MIME{Symbol("text/plain")}, ::Array{LibBSON.BSONObject,1}) at ./REPL.jl:132
in display(::Base.REPL.REPLDisplay{Base.REPL.LineEditREPL}, ::Array{LibBSON.BSONObject,1}) at ./REPL.jl:135
in display(::Array{LibBSON.BSONObject,1}) at ./multimedia.jl:143
in print_response(::Base.Terminals.TTYTerminal, ::Any, ::Void, ::Bool, ::Bool, ::Void) at ./REPL.jl:154
in print_response(::Base.REPL.LineEditREPL, ::Any, ::Void, ::Bool, ::Bool) at ./REPL.jl:139
in (::Base.REPL.##22#23{Bool,Base.REPL.##33#42{Base.REPL.LineEditREPL,Base.REPL.REPLHistoryProvider},Base.REPL.LineEditREPL,Base.LineEdit.Prompt})(::Base.LineEdit.MIState, ::Base.AbstractIOBuffer{Array{UInt8,1}}, ::Bool) at ./REPL.jl:652
in run_interface(::Base.Terminals.TTYTerminal, ::Base.LineEdit.ModalInterface) at ./LineEdit.jl:1579
in run_interface(::Base.Terminals.TTYTerminal, ::Base.LineEdit.ModalInterface) at /Applications/Julia-0.5.app/Contents/Resources/julia/lib/julia/sys.dylib:?
in run_frontend(::Base.REPL.LineEditREPL, ::Base.REPL.REPLBackendRef) at ./REPL.jl:903
in run_repl(::Base.REPL.LineEditREPL, ::Base.##950#951) at ./REPL.jl:188
in _start() at ./client.jl:363
in _start() at /Applications/Julia-0.5.app/Contents/Resources/julia/lib/julia/sys.dylib:?