[FillStyle] in drDefinePacket is optional

[EugeneZelenko]

I re-wrote import_tf on Python and tried it on real-world files. It turned out that [FillStyle] was not presented in drDefinePacket. My workaround was:

packets[defs[1]] = [ defs[2], defs[3], defs[4], defs[5], defs[6] if len(defs) > 6 else None ]