Bug 1638559 - return a deny action when the window context is null. r=bryce

I suspect that when enabling Fission, in some situation, we might get a null window context which results in a crash. Therefore, returning a deny action if we are not able to get a window context.

Differential Revision: https://phabricator.services.mozilla.com/D76196

dom/media/AutoplayPolicy.cpp

@@ -60,9 +60,13 @@ static uint32_t SiteAutoplayPerm(nsPIDOMWindowInner* aWindow) {
   if (!aWindow || !aWindow->GetBrowsingContext()) {
     return nsIPermissionManager::DENY_ACTION;
   }
-  return aWindow->GetBrowsingContext()
-      ->GetTopWindowContext()
-      ->GetAutoplayPermission();
+
+  WindowContext* topContext =
+      aWindow->GetBrowsingContext()->GetTopWindowContext();
+  if (!topContext) {
+    return nsIPermissionManager::DENY_ACTION;
+  }
+  return topContext->GetAutoplayPermission();
 }
 
 static bool IsWindowAllowedToPlay(nsPIDOMWindowInner* aWindow) {