Currently, sequencer structs contain several pointers to data within
other structs. These pointers need to be remapped as the structs are
reallocated when reading from blend files. That has worked so far
because the pointers are exactly the values from the Blender session
that saved the file. WIth the implementation of #127706, the pointers
in the file aren't "real" anymore, and we can't offset them to get the
struct that contained the data.
This commit replaces these 4 mid-struct pointers to point to the
containing strips instead, and uses some trivial logic to access the
fallback root sequence channels and strips. This makes the pointer
remapping on file load possible again.
The downside is that this isn't strictly backward or forward compatible,
but only on a UI-level. The active meta-strip information will be lost,
and the sequencer will reset to displaying the root sequence.
Depends on #144624
Pull Request: https://projects.blender.org/blender/blender/pulls/144626
58554964e4