On client, when game ends locally set turn to -1 (nobody) so that

display won't be confusing during the interval before the server
receives the move and responds with a game-over message.

xwords4/common/server.c

@@ -1927,6 +1927,7 @@ nextTurn( ServerCtxt* server, XP_S16 nxtTurn )
         } else {
             XP_LOGF( "%s: Doing nothing; waiting for server to end game", 
                      __func__ );
+            setTurn( server, -1 );
             /* I'm the client. Do ++nothing++. */
         }
     }