Check IDemoRecorder pointer before use

If the pointer to the IDemoRecorder instance fails to be found after an
update, don't try to use it blindly, but check if it's not null before..

hltvserverwrapper.cpp

@@ -376,7 +376,7 @@ HLTVServerWrapper *HLTVServerWrapperManager::GetWrapper(IDemoRecorder *demorecor
 	for (unsigned int i = 0; i < m_HLTVServers.length(); i++)
 	{
 		HLTVServerWrapper *wrapper = m_HLTVServers[i];
-		if (wrapper->GetDemoRecorder() == demorecorder)
+		if (wrapper->GetDemoRecorder() != nullptr && wrapper->GetDemoRecorder() == demorecorder)
 			return wrapper;
 	}
 	return nullptr;