This also fixes crash when deleting keys.
Issue was caused by incorrect implementation of batch deleting with
`SEQ_retiming_remove_multiple_keys()` function. It tried to remove data
from different strips, when it should work with one strip at the time.
Also transitions and freeze frames were treated as normal keys, but they
do need special handling.
Pull Request: https://projects.blender.org/blender/blender/pulls/116722
534a1c9ecd