Error when no-same-dimensions and not all frames have the same extension

[IsaacBerman]

Describe the bug

• When not all frames have the same extension, and no-same-dimensions is set, there will be an error as filename will mismatch

To Reproduce Steps to reproduce the behavior:

1. Set no-same-dimensions flag
2. Use image folder that has files with different extensions
3. See error

Expected behavior

• Should use whatever extension of image when moving/downscaling, not just take the first in dir

Screenshots

[IsaacBerman]

To add to this -- an error still occurs even if all files have same extension.