Language client: fixed crash when closing files before autocomplete is set

src/source_language_protocol.cpp

@@ -421,9 +421,11 @@ void Source::LanguageProtocolView::close() {
   if(initialize_thread.joinable())
     initialize_thread.join();
 
+  if(autocomplete) {
     autocomplete->state = Autocomplete::State::idle;
     if(autocomplete->thread.joinable())
       autocomplete->thread.join();
+  }
 
   thread_pool.shutdown(true);