88a6df24aa
Before bd00324c26, strip lengths were changed in
`rna_NlaStrip_frame_start_ui_set` and `rna_NlaStrip_frame_end_ui_set`
so as not to be shorter than NLASTRIP_MIN_LEN_THRESH.
This prevented `BKE_nlameta_flush_transforms` from working with
zero-length strips.
But now, in some cases, strip can be zero length.
Therefore, consider this case and avoid division by zero.
Pull Request: https://projects.blender.org/blender/blender/pulls/110121