Rebuilding a `ConditionalDimension` with no factor adds a factor.

[EdCaunt]

If a ConditionalDimension is created with factor=None, then self._factor is set to None, but self.factor will return 1. As such, when rebuilding a ConditionalDimension with no factor, a factor of 1 is added unexpectedly, changing the generated code.

[georgebisbas]

Is there an MFE for this?

[EdCaunt]

Create a ConditionalDimension with a condition but no factor, then compare cd._factor to cd._rebuild()._factor