Fix (unreported): Memory leak when adding strip in VSE

Using unsupported movie file when adding movie strip causes memory leak.

Pull Request: https://projects.blender.org/blender/blender/pulls/109078

source/blender/editors/space_sequencer/sequencer_add.cc

@@ -972,6 +972,7 @@ static int sequencer_add_movie_strip_exec(bContext *C, wmOperator *op)
   }
 
   if (SEQ_collection_len(movie_strips) == 0) {
+    sequencer_add_cancel(C, op);
     SEQ_collection_free(movie_strips);
     return OPERATOR_CANCELLED;
   }