[api] Fix crash loop on VoiceAssistantConfigurationRequest (#16757)

esphome/components/api/api_connection.cpp

@@ -1306,6 +1306,9 @@ void APIConnection::on_voice_assistant_announce_request(const VoiceAssistantAnno
 bool APIConnection::send_voice_assistant_get_configuration_response_(const VoiceAssistantConfigurationRequest &msg) {
   VoiceAssistantConfigurationResponse resp;
   if (!this->check_voice_assistant_api_connection_()) {
+    // send_message encodes synchronously, so this stack local outlives the encode
+    const std::vector<std::string> empty_wake_words;
+    resp.active_wake_words = &empty_wake_words;
     return this->send_message(resp);
   }