cordon off hydration code

packages/svelte/src/internal/client/dom/blocks/each.js

@@ -218,9 +218,12 @@ export function each(node, flags, get_collection, get_key, render_fn, fallback_f
 			}
 		}
 
-		if (!hydrating) {
+		if (hydrating) {
-			reconcile(array, state, anchor, render_fn, flags, get_key, get_collection);
+			if (length === 0 && fallback_fn) {
+				fallback = branch(() => fallback_fn(anchor));
 			}
+		} else {
+			reconcile(array, state, anchor, render_fn, flags, get_key, get_collection);
 
 			if (fallback_fn !== null) {
 				if (length === 0) {
@@ -235,6 +238,7 @@ export function each(node, flags, get_collection, get_key, render_fn, fallback_f
 					});
 				}
 			}
+		}
 
 		if (mismatch) {
 			// continue in hydration mode