Fix ads script loading - store error to reject on subsequent calls

The previous code never resolved or rejected after the ads script tag
failed to load once

src/js/ads.js

@@ -1,6 +1,7 @@
 /* global google */
 
 let sdkScriptLoaded = false;
+let sdkScriptError = null;
 
 function createVideoOverlayElement() {
 	const overlayEl = document.createElement('div');
@@ -36,13 +37,16 @@ class VideoAds {
 
 			if (sdkScriptLoaded || window.google && window.google.ima) {
 				resolve();
+			} else if (sdkScriptError) {
+				reject(sdkScriptError);
 			} else {
 				googleSdkScript.addEventListener('load', () => {
 					sdkScriptLoaded = true;
 					resolve();
 				});
 
 				googleSdkScript.addEventListener('error', (e) => {
+					sdkScriptError = e;
 					reject(e);
 				});
 			}