tweak

packages/svelte/src/internal/client/transitions.js

@@ -439,19 +439,21 @@ function create_transition(dom, init, direction, effect) {
 					// If we are working with CSS animations, then before we call reverse, we also need to ensure
 					// that we reverse the easing logic. To do this we need to re-create the keyframes so they're
 					// in reverse with easing properly reversed too.
-					if (payload !== null && payload.css !== undefined) {
+					if (
+						payload !== null &&
+						payload.css !== undefined &&
+						/** @type {Animation} */ (animation).effect != null
+					) {
 						const duration = payload.duration ?? 300;
 						const css_fn = payload.css;
 						const easing_fn = payload.easing || linear;
 						const keyframes = create_keyframes(easing_fn, css_fn, duration, direction, true);
-						if (/** @type {Animation} */ (animation).effect != null) {
-							// If we have an existing animation, we need to pause it and create a new animation
-							// with the new frames.
-							animation.pause();
-							create_animation();
-							// @ts-ignore
-							animation.effect.setKeyframes(keyframes);
-						}
+						// If we have an existing animation, we need to pause it and create a new animation
+						// with the new frames.
+						animation.pause();
+						create_animation();
+						// @ts-ignore
+						animation.effect.setKeyframes(keyframes);
 					}
 					/** @type {Animation | TickAnimation} */ (animation).reverse();
 				} else {