fix some type errors

packages/svelte/src/internal/client/dom/operations.js

@@ -85,17 +85,13 @@ export function first_child(fragment, is_text) {
 	// text node to hydrate — we must therefore create one
 	if (is_text && hydrate_start?.nodeType !== 3) {
 		var text = empty();
-		// var dom = /** @type {import('#client').TemplateNode[]} */ (
-		// 	/** @type {import('#client').Effect} */ (current_effect).dom
-		// );
+		var effect = /** @type {import('#client').Effect} */ (current_effect);
 
-		if (current_effect.nodes.start === hydrate_start) {
-			current_effect.nodes.start = text;
+		if (effect.nodes?.start === hydrate_start) {
+			effect.nodes.start = text;
 		}
 
-		// dom.unshift(text);
 		hydrate_start?.before(text);
-
 		return text;
 	}