Fix T55034: Setting duplication group for multiple selected items only

affects one item

UI editing multiple selected items missed the case of PROP_POINTER
properties

Reviewed By: campbellbarton

Differential Revision: https://developer.blender.org/D3373

source/blender/editors/interface/interface_handlers.c

@@ -1560,6 +1560,7 @@ static void ui_selectcontext_apply(
 			bool  b;
 			int   i;
 			float f;
+			PointerRNA p;
 		} delta, min, max;
 
 		const bool is_array = RNA_property_array_check(prop);
@@ -1584,6 +1585,9 @@ static void ui_selectcontext_apply(
 				delta.b = RNA_property_boolean_get(&but->rnapoin, prop);  /* not a delta infact */
 			}
 		}
+		else if (rna_type == PROP_POINTER) {
+			delta.p = RNA_property_pointer_get(&but->rnapoin, prop);  /* not a delta infact */
+		}
 
 #ifdef USE_ALLSELECT_LAYER_HACK
 		/* make up for not having 'handle_layer_buttons' */
@@ -1656,6 +1660,10 @@ static void ui_selectcontext_apply(
 				BLI_assert(!is_array);
 				RNA_property_enum_set(&lptr, lprop, other_value);
 			}
+			else if (rna_type == PROP_POINTER) {
+				const PointerRNA other_value = delta.p;
+				RNA_property_pointer_set(&lptr, lprop, other_value);
+			}
 
 			RNA_property_update(C, &lptr, prop);
 		}