Fixed value check in property assignment

[HalfWhitt]

Prior to the dataclass restructuring, property assignment checked against getattr(self, "_%s" % name, initial) to see if a change had occurred and the property would need to be applied. I overlooked this and used None as the default instead of initial.

This didn't really make anything work incorrectly; however, a previously unassigned property being assigned a value equal to its initial value then triggers an unnecessary apply.

I've reverted it to getattr(obj, f"_{self.name}", self.initial).

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[freakboy3742]

Good catch - thanks for the fix!