Fixes Assbin import code when reading strings from binary format. The string gets created, and the data gets read in - but the string never ends up being null-terminated, and using the aiString::CString() method results in a lot of garbled data being returned along with the desired value. If the length is 0 - we short circuit out because it caused further issues when reading certain strings from MS3D file format. Otherwise, the string gets null terminated at it's length.