WM: avoid unnecessary undo step creation when duplicating

Calling duplicate operation without selecting anything registers an undo
step. If nothing is selected (keyframe, curve, object, etc.), cancel the
operator execution to prevent undo push.

Patch improves following operators:

- ACTION_OT_duplicate
- GPENCIL_OT_duplicate
- GRAPH_OT_duplicate
- MESH_OT_duplicate
- NODE_OT_duplicate
- OBJECT_OT_duplicate

Reviewed By: campbellbarton

Ref D14511

source/blender/editors/mesh/editmesh_tools.c

@@ -2014,6 +2014,7 @@ static int edbm_duplicate_exec(bContext *C, wmOperator *op)
   uint objects_len = 0;
   Object **objects = BKE_view_layer_array_from_objects_in_edit_mode_unique_data(
       view_layer, CTX_wm_view3d(C), &objects_len);
+  bool changed = false;
 
   for (uint ob_index = 0; ob_index < objects_len; ob_index++) {
     Object *obedit = objects[ob_index];
@@ -2024,6 +2025,7 @@ static int edbm_duplicate_exec(bContext *C, wmOperator *op)
 
     BMOperator bmop;
     BMesh *bm = em->bm;
+    changed = true;
 
     EDBM_op_init(em,
                  &bmop,
@@ -2058,16 +2060,16 @@ static int edbm_duplicate_exec(bContext *C, wmOperator *op)
   }
   MEM_freeN(objects);
 
-  return OPERATOR_FINISHED;
+  return (changed) ? OPERATOR_FINISHED : OPERATOR_CANCELLED;
 }
 
 static int edbm_duplicate_invoke(bContext *C, wmOperator *op, const wmEvent *UNUSED(event))
 {
   WM_cursor_wait(true);
-  edbm_duplicate_exec(C, op);
+  const int retval = edbm_duplicate_exec(C, op);
   WM_cursor_wait(false);
 
-  return OPERATOR_FINISHED;
+  return retval;
 }
 
 void MESH_OT_duplicate(wmOperatorType *ot)