Since stone age of lib_query, the code would iterate over the current list of active sequences (from a meta strip e.g.), and not over the whole list of those. This is a critical issue as it means in some cases (editing a meta strip typically), some ID pointers would be missed/ignored by this foreach looper, which is now at the center of most of our ID management code. This caused a bug here at the studio, leading to loss of all sound IDs used by sound strips when editing and undoing inside a meta strip, since ID refcounting would not happen properly on strips using sounds outside the meta-strip context during file reading of the undo steps. To be backported to 2.83. Differential Revision: https://developer.blender.org/D8671