Bug 1602318 - Make sure rv is initialized correctly in all branches of OpenInitializedChannel. r=nika

Differential Revision: https://phabricator.services.mozilla.com/D70621

docshell/base/nsDocShell.cpp

@@ -10053,6 +10053,7 @@ nsresult nsDocShell::OpenInitializedChannel(nsIChannel* aChannel,
     // ClientInfo, so we just need to allocate a corresponding ClientSource.
     CreateReservedSourceIfNeeded(aChannel,
                                  win->EventTargetFor(TaskCategory::Other));
+    rv = NS_OK;
   } else {
     rv = AddClientChannelHelper(aChannel, std::move(noReservedClient),
                                 GetInitialClientInfo(),