Error re-registering add-on (with fix)

[ideasman42]

If you un-register and re-register this add-on, there is an error:
pcb2blender_importer/__init__.py

ValueError: register_class(...): already registered as a subclass 'PCB2BLENDER_OT_import_pcb3d'

This is caused by the register function always adding to _modules.

To fix this, at the start of register(..) in pcb2blender_importer/__init__.py run: _modules.clear() .

[30350n]

Fixed! Thanks for catching that and providing the fix ^^