Fix crash on bin clip deletion with instance on locked track

BUG: 459260

src/bin/projectclip.cpp

@@ -1967,7 +1967,9 @@ bool ProjectClip::selfSoftDelete(Fun &undo, Fun &redo)
         }
         if (auto timeline = clip.second.lock()) {
             timeline->requestClipUngroup(clip.first, undo, redo);
-            timeline->requestItemDeletion(clip.first, undo, redo, true);
+            if (!timeline->requestItemDeletion(clip.first, undo, redo, true)) {
+                return false;
+            }
         } else {
             qDebug() << "Error while deleting clip: timeline unavailable";
             Q_ASSERT(false);

src/bin/projectitemmodel.cpp

@@ -674,7 +674,9 @@ bool ProjectItemModel::requestBinClipDeletion(const std::shared_ptr<AbstractProj
         binId = ptr->clipId();
     }
     bool isSubClip = clip->itemType() == AbstractProjectItem::SubClipItem;
-    clip->selfSoftDelete(undo, redo);
+    if (!clip->selfSoftDelete(undo, redo)) {
+        return false;
+    }
     int id = clip->getId();
     Fun operation = removeItem_lambda(id);
     Fun reverse = addItem_lambda(clip, parentId);