Actually it wasn't a bug -- currently curve/dopesheet view are in separated
spaces, so to keep displaying data in sync it's needed to update all visible
clip editors when changing displaying clip datablock.
Changed logic here a bit, so current clip wouldn't be changes for clip editors
where view is set to CLIP, only dopesheet/graph views are getting updated.
Also do not update displaying clip datablock when changing it from curve/dopesheet.