Effects are applied only on the "top" clip
Submitted by Jeff F.T.
Assigned to Mathieu Duponchelle
Let's say you have two clips on top of other with transparency/alpha/chroma keying.
If you apply an effect to the clip below, the effect is (incorrectly) applied to the clip "on the top" instead.
Imported from https://bugzilla.gnome.org/show_bug.cgi?id=641358