Fix the reconnect button

After a membership manager error, clicking the 'reconnect' button did nothing. This is because we were forgetting to clear the external error state, causing it to transition directly back to the same error state.

src/room/GroupCallView.tsx

@@ -502,10 +502,11 @@ export const GroupCallView: FC<Props> = ({
   return (
     <GroupCallErrorBoundary
       widget={widget}
-      recoveryActionHandler={(action) => {
+      recoveryActionHandler={async (action) => {
+        setExternalError(null);
         if (action == "reconnect") {
           setLeft(false);
-          enterRTCSessionOrError(rtcSession).catch((e) => {
+          await enterRTCSessionOrError(rtcSession).catch((e) => {
             logger.error("Error re-entering RTC session", e);
           });
         }