Note that these changes are limited simple cases as these kinds of
changes could allow for errors when refactoring code when the known
state is not so obvious.
Use LISTBASE_FOREACH instead.
SEQ_CURRENT_BEGIN did null checks, so now these must be explicit.
Reviewed By: campbellbarton
Differential Revision: https://developer.blender.org/D10823
Build proxies automatically when added to sequencer timeline and when
switching preview size.
This behavior can be disabled in user preferences.
Reviewed By: sergey, fsiddi
Differential Revision: https://developer.blender.org/D10363
Building proxy with meta strip selected resulted in attempt to render
meta strip itself and save result as image as is done when building
image proxies.
Remove meta strip from list of supported strips.
Multicam, Meta and scene strip are cleared from poll function in UI as well.
Reviewed By: sergey
Differential Revision: https://developer.blender.org/D10001
