Mix: Fix first clip out not correctly reset on second clip deletion

src/timeline2/model/timelinemodel.cpp

@@ -1840,6 +1840,12 @@ bool TimelineModel::requestClipDeletion(int clipId, Fun &undo, Fun &redo)
                 res = getTrackById(trackId)->requestRemoveMix({clipId, mixData.secondClipId}, undo, redo);
             }
         }
+        if (getTrackById_const(trackId)->hasStartMix(clipId)) {
+            MixInfo mixData = getTrackById_const(trackId)->getMixInfo(clipId).first;
+            if (isClip(mixData.firstClipId)) {
+                res = getTrackById(trackId)->requestRemoveMix({mixData.firstClipId, clipId}, undo, redo);
+            }
+        }
         res = res && getTrackById(trackId)->requestClipDeletion(clipId, true, !m_closing, undo, redo, false, true);
         if (!res) {
             undo();