Fix `is_inside_tree` error when inspecting an Environment resource
@@ -636,7 +636,7 @@ void EditorSpinSlider::_grabber_mouse_exited() {
void EditorSpinSlider::set_read_only(bool p_enable) {
read_only = p_enable;
- if (read_only && value_input) {
+ if (read_only && value_input && value_input->is_inside_tree()) {
value_input->release_focus();
}