NumberedObjectCollection append_renumber ignores negative numbers

[MicahGale]

Describe the bug

NumberedObjectCollection.append_renumber (e.g., Cells.append_renumber) considers -1 a valid number. This is the placeholder value, that shouldn't be used.

To Reproduce

import montepy
mat= montepy.Material()
mats = montepy.materials.Materials()
mats.append_renumber(mat)
print(mat.number)

yields

-1

Version

• Version 0.5.3, 1.0.0a1