This was caused by canceling operator if strip has more than 0 inputs.
Logic should be reversed - cancel only if strip has 0 inputs.
BKE_sequencer_render_loop_check() arguments had to be sanitized because
seq_effect_find_selected() can set seq1,2,3 to NULL
Reviewed By: sergey
Differential Revision: https://developer.blender.org/D9197
Generic ID management code can now do those local temp copy handling, so
no need for duplicated own code for that.
No behavioral changes expected here.
This is first step of refactoring task T77580.
Next step will be breaking up files into smaller ones.
Reviewed By: sergey, brecht
Differential Revision: https://developer.blender.org/D8492
