Fix a crash with Universal Links.

Nil-check the URL before feeding it to the Universal Link API.

Bug: 1051802
Change-Id: I357880d0ffbd512de85c50a461f01fdd8ba238a5
Reviewed-on: https://chromium-review.googlesource.com/c/chromium/src/+/2062253
Commit-Queue: Avi Drissman <avi@chromium.org>
Commit-Queue: Robert Sesek <rsesek@chromium.org>
Auto-Submit: Avi Drissman <avi@chromium.org>
Reviewed-by: Robert Sesek <rsesek@chromium.org>
Cr-Commit-Position: refs/heads/master@{#742196}

chrome/browser/apps/intent_helper/mac_apps_navigation_throttle.mm

@@ -57,8 +57,11 @@ SFUniversalLink* API_AVAILABLE(macos(10.15)) GetUniversalLink(const GURL& url) {
   if (!safari_services || !SFUniversalLink_class)
     return nil;
 
-  return [[[SFUniversalLink_class alloc]
-      initWithWebpageURL:net::NSURLWithGURL(url)] autorelease];
+  NSURL* nsurl = net::NSURLWithGURL(url);
+  if (!nsurl)
+    return nil;
+
+  return [[[SFUniversalLink_class alloc] initWithWebpageURL:nsurl] autorelease];
 }
 
 base::Optional<IntentPickerAppInfo> AppInfoForUrl(const GURL& url) {