Fix for bug#11758931 - 51196: SLAVE SQL: GOT AN ERROR WRITING

COMMUNICATION PACKETS, ERROR_CODE: 1160

Addendum: for some queries table->in_use might be NULL -
check it.

storage/federated/ha_federated.cc

@@ -1658,6 +1658,7 @@ int ha_federated::close(void)
     if the original query was not issued against the FEDERATED table.
     So, don't propagate errors from mysql_close().
   */
+  if (table->in_use)
     table->in_use->clear_error();
 
   DBUG_RETURN(free_share(share));