Object Mode: only toggle active object mode once

- When toggling a mode that doesn't support multi editing
  only do this once of the active object.

- For sculpt mode create sculpt data since this is needed
  for activating other sculpt objects on reload.

source/blender/blenkernel/BKE_object.h

@@ -293,6 +293,8 @@ void BKE_object_handle_update_ex(
         const bool do_proxy_update);
 void BKE_object_sculpt_modifiers_changed(struct Object *ob);
 
+void BKE_object_sculpt_data_create(struct Object *ob);
+
 int BKE_object_obdata_texspace_get(struct Object *ob, short **r_texflag, float **r_loc, float **r_size, float **r_rot);
 
 struct Mesh *BKE_object_get_evaluated_mesh(const struct Depsgraph *depsgraph, struct Object *ob);

source/blender/blenkernel/intern/object.c

@@ -2959,6 +2959,13 @@ void BKE_object_handle_update(Depsgraph *depsgraph, Scene *scene, Object *ob)
 	BKE_object_handle_update_ex(depsgraph, scene, ob, NULL, true);
 }
 
+void BKE_object_sculpt_data_create(Object *ob)
+{
+	BLI_assert(ob->mode & OB_MODE_ALL_SCULPT);
+	ob->sculpt = MEM_callocN(sizeof(SculptSession), __func__);
+	ob->sculpt->mode_type = ob->mode;
+}
+
 void BKE_object_sculpt_modifiers_changed(Object *ob)
 {
 	SculptSession *ss = ob->sculpt;

source/blender/blenloader/intern/readfile.c

@@ -5648,8 +5648,7 @@ static void direct_link_object(FileData *fd, Object *ob)
 	if (ob->sculpt) {
 		/* Only create data on undo, otherwise rely on editor mode switching. */
 		if (fd->memfile && (ob->mode & OB_MODE_ALL_SCULPT)) {
-			ob->sculpt = MEM_callocN(sizeof(SculptSession), "reload sculpt session");
-			ob->sculpt->mode_type = ob->mode;
+			BKE_object_sculpt_data_create(ob);
 		}
 		else {
 			ob->sculpt = NULL;

source/blender/editors/util/ed_util.c

@@ -130,7 +130,17 @@ void ED_editors_init(bContext *C)
 							ED_object_posemode_enter_ex(bmain, ob);
 						}
 						else {
-							ED_object_mode_toggle(C, mode);
+							if (obact == ob) {
+								ED_object_mode_toggle(C, mode);
+							}
+							else {
+								/* Create data for non-active objects which need it for
+								 * mode-switching but don't yet support multi-editing. */
+								if (mode & OB_MODE_ALL_SCULPT) {
+									ob->mode = mode;
+									BKE_object_sculpt_data_create(ob);
+								}
+							}
 						}
 					}
 				}