Fixes the stopping of animation effects in bbcode after appending

(cherry picked from commit 88b30a29bf6f5497b1f42e33c6dfbff795fd5585)

scene/gui/rich_text_label.cpp

@@ -2458,6 +2458,17 @@ Error RichTextLabel::append_bbcode(const String &p_bbcode) {
 		}
 	}
 
+	Vector<ItemFX *> fx_items;
+	for (List<Item *>::Element *E = main->subitems.front(); E; E = E->next()) {
+		Item *subitem = static_cast<Item *>(E->get());
+		_fetch_item_fx_stack(subitem, fx_items);
+
+		if (fx_items.size()) {
+			set_process_internal(true);
+			break;
+		}
+	}
+
 	return OK;
 }