Is it related or a new issue?
To me it looks like a new issue.
<type 'exceptions.IOError'>: Invalid project file /home/f3nix/devel/LULZBOT/TAZ 5 - FreeCAD/Test 2/TAZ 5 Final Assembly V0.1.fcstd: basic_string::_M_construct null not valid
To me it looks like a null pointer is assigned to a std::string which is not allowed. But funny that it raises an exception instead of crashing immediately. Do you get this error only with "TAZ 5 Final Assembly V0.1.fcstd" or any other project file?
Hi, I have the very same issue with qt5 builds on arch linux and ubuntu 16.04. However, I can't open any file which contains objects from the part or partdesign workbench. Didn't test all workbenches but it doesn't happen for files containing only spreadsheets. Workarounds from f3nix work for me too.