`NLASTRIP_TYPE_TRANSITION` was being used incorrectly as a flag, having
`NLASTRIP_TYPE_TRANSITION=1` and `NLASTRIP_TYPE_SOUND=3` in the enum
`eNlaStrip_Type`, when evaluating `NLASTRIP_TYPE_SOUND &
NLASTRIP_TYPE_TRANSITION` gives a invalid truish value.
Also `strips` that can't be placed were freed, but no removed from the
`strips list`, this will cause a error if the `strip` is at begin
or end of the list.
Pull Request: https://projects.blender.org/blender/blender/pulls/110605
5b3398a673