Fix: [Script] Only show debug script window at the end of savegame loading (#12135)

(cherry picked from commit 2d7ad9f717)

src/ai/ai_instance.cpp

@@ -63,6 +63,9 @@ void AIInstance::Died()
 	/* Intro is not supposed to use AI, but it may have 'dummy' AI which instant dies. */
 	if (_game_mode == GM_MENU) return;
 
+	/* Don't show errors while loading savegame. They will be shown at end of loading anyway. */
+	if (_switch_mode != SM_NONE) return;
+
 	ShowScriptDebugWindow(_current_company);
 
 	const AIInfo *info = AIConfig::GetConfig(_current_company)->GetInfo();