Original code was very confusing, with seemingly indecisive logic.
I hope, that it is less confusing now, however there is still some
indecisiveness present. This is because multiview configuration may not
be correct, so there must be fallback and only some multiview settings
require loading of multiple files. Perhaps be better wording could be
used for `open_anim_file_multiview()`.
Fortunately this is now expressed within 5 lines of code instead of 100.
Further this can be improved by checking if the file exists, since now
VSE crashes when right eye image is missing, because loading code
does not try to actually open the file.
Pull Request: https://projects.blender.org/blender/blender/pulls/118580
d4925b9775