fix warnings

examples/widgets/btn/lv_example_btn_2.c

@@ -48,7 +48,6 @@ void lv_example_btn_2(void)
     static lv_style_transition_dsc_t trans;
     static lv_style_prop_t props[] = {LV_STYLE_OUTLINE_WIDTH, LV_STYLE_OUTLINE_OPA, 0};
     lv_style_transition_dsc_init(&trans, props, lv_anim_path_linear, 300, 0);
-    trans.user_data = &trans;
 
     lv_style_set_transition(&style_pr, &trans);
 

src/core/lv_obj_class.c

@@ -51,6 +51,8 @@ lv_obj_t * lv_obj_class_create_obj(const lv_obj_class_t * class_p, lv_obj_t * pa
     obj->parent = parent;
 #if LV_USE_USER_DATA
     obj->user_data = user_data;
+#else
+    LV_UNUSED(user_data);
 #endif
 
     /*Create a screen*/