From 03f166117693c6daccb0bf46cf20464cbd3afae6 Mon Sep 17 00:00:00 2001
From: Matteo Battista <matteo.battista@gmail.com>
Date: Wed, 30 Apr 2025 08:47:21 +0200
Subject: [PATCH] fix: update_branch with (anchor).data possible undefined

---
 packages/svelte/src/internal/client/dom/blocks/if.js | 1 +
 1 file changed, 1 insertion(+)

diff --git a/packages/svelte/src/internal/client/dom/blocks/if.js b/packages/svelte/src/internal/client/dom/blocks/if.js
index 925abb9d9d46..2f408c009c82 100644
--- a/packages/svelte/src/internal/client/dom/blocks/if.js
+++ b/packages/svelte/src/internal/client/dom/blocks/if.js
@@ -57,6 +57,7 @@ export function if_block(node, fn, [root_index, hydrate_index] = [0, 0]) {
 		if (hydrating && hydrate_index !== -1) {
 			if (root_index === 0) {
 				const data = /** @type {Comment} */ (anchor).data;
+				if (!data) return;
 				if (data === HYDRATION_START) {
 					hydrate_index = 0;
 				} else if (data === HYDRATION_START_ELSE) {