LibOverride: Remove an override property when it has no operations.

Update #BKE_lib_override_library_id_unused_cleanup to also clear the
property when all its operations have been removed, even if the
property itself was not tagged as unused.

source/blender/blenkernel/intern/lib_override.cc

@@ -4571,6 +4571,9 @@ void BKE_lib_override_library_id_unused_cleanup(ID *local)
             BKE_lib_override_library_property_operation_delete(op, opop);
           }
         }
+        if (BLI_listbase_is_empty(&op->operations)) {
+          BKE_lib_override_library_property_delete(local->override_library, op);
+        }
       }
     }
   }