fix problem at shutdown

panda/src/pstatclient/pStatClient.cxx

@@ -372,6 +372,11 @@ void PStatClient::
 client_main_tick() {
   LightReMutexHolder holder(_lock);
   if (has_impl()) {
+    if (!_impl->client_is_connected()) {
+      client_disconnect();
+      return;
+    }
+
     _impl->client_main_tick();
 
     MultiThingsByName::const_iterator ni =

panda/src/pstatclient/pStatClientImpl.cxx

@@ -458,7 +458,7 @@ handle_server_control_message(const PStatServerControlMessage &message) {
 void PStatClientImpl::
 connection_reset(const PT(Connection) &connection, bool) {
   if (connection == _tcp_connection) {
-    _client->client_disconnect();
+    client_disconnect();
   } else if (connection == _udp_connection) {
     pstats_cat.warning()
       << "Trouble sending UDP; switching to TCP only.\n";