fix: prevent div/0 when generating transition keyframes (#13058)

closes #13047

.changeset/few-walls-check.md

@@ -0,0 +1,5 @@
+---
+'svelte': patch
+---
+
+fix: prevent div/0 when generating transition keyframes

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

@@ -358,6 +358,7 @@ function animate(element, options, counterpart, t2, on_finish) {
 		var duration = /** @type {number} */ (options.duration) * Math.abs(delta);
 		var keyframes = [];
 
+		if (duration > 0) {
 			if (css) {
 				var n = Math.ceil(duration / (1000 / 60)); // `n` must be an integer, or we risk missing the `t2` value
 
@@ -368,14 +369,6 @@ function animate(element, options, counterpart, t2, on_finish) {
 				}
 			}
 
-		animation = element.animate(keyframes, { duration, fill: 'forwards' });
-
-		animation.onfinish = () => {
-			get_t = () => t2;
-			tick?.(t2, 1 - t2);
-			on_finish();
-		};
-
 			get_t = () => {
 				var time = /** @type {number} */ (
 					/** @type {globalThis.Animation} */ (animation).currentTime
@@ -394,6 +387,15 @@ function animate(element, options, counterpart, t2, on_finish) {
 					return true;
 				});
 			}
+		}
+
+		animation = element.animate(keyframes, { duration, fill: 'forwards' });
+
+		animation.onfinish = () => {
+			get_t = () => t2;
+			tick?.(t2, 1 - t2);
+			on_finish();
+		};
 	};
 
 	return {