Hatch fill fails on certain object types

[oskay]

Hatch fill really works on paths only.

Testing a file that contains a polygon object produces a traceback:

  File "/Users/me/Library/Application Support/org.inkscape.Inkscape/config/inkscape/extensions/axidraw_deps/axidrawinternal/eggbot_hatch.py", line 710, in addPathVertices
    sp = simplepath.parsePath(path)
  File "/Users/me/Library/Application Support/org.inkscape.Inkscape/config/inkscape/extensions/axidraw_deps/ink_extensions/simplepath.py", line 116, in parsePath
    raise Exception('Invalid number of parameters')
Exception: Invalid number of parameters

As a full rewrite of Hatch Fill is planned, we should probably not implement all object types here, but instead add a warning about using Object to Path rather than have a traceback.

[oskay]

I've been unable to reproduce this lately; if someone has a test case that shows a traceback here, that would be helpful.