Qt: Fix power off button not exiting in batch mode

src/duckstation-qt/qthostinterface.cpp

@@ -765,13 +765,7 @@ void QtHostInterface::powerOffSystem()
     return;
   }
 
-  if (System::IsShutdown())
-    return;
-
-  if (g_settings.save_state_on_exit)
-    SaveResumeSaveState();
-
-  DestroySystem();
+  PowerOffSystem();
 }
 
 void QtHostInterface::synchronousPowerOffSystem()

src/frontend-common/common_host_interface.cpp

@@ -183,6 +183,9 @@ void CommonHostInterface::DestroySystem()
 
 void CommonHostInterface::PowerOffSystem()
 {
+  if (System::IsShutdown())
+    return;
+
   if (g_settings.save_state_on_exit)
     SaveResumeSaveState();