Add missing return

src/vs/workbench/contrib/webview/browser/pre/host.js

@@ -37,7 +37,7 @@
 
 	const workerReady = new Promise(async (resolveWorkerReady) => {
 		if (!navigator.serviceWorker) {
-			resolveWorkerReady();
+			return resolveWorkerReady();
 		}
 
 		const expectedWorkerVersion = 1;