Fix issue with the current tab not being saved through screen recreation

Common/UI/TabHolder.cpp

@@ -209,7 +209,10 @@ bool TabHolder::SetCurrentTab(int tab, bool skipTween) {
 	tabs_[tab]->SetVisibility(V_VISIBLE);
 
 	currentTab_ = tab;
-
+	UI::EventParams e{};
+	e.v = this;
+	e.a = currentTab_;
+	OnChangeTab.Trigger(e);
 	return created;
 }
 

Common/UI/TabHolder.h

@@ -52,6 +52,8 @@ public:
 	}
 	bool EnsureTab(int index);  // return true if it actually created a tab.
 
+	Event OnChangeTab;
+
 private:
 	void AddTabContents(std::string_view title, ImageID imageId, ViewGroup *tabContents);
 	void OnTabClick(EventParams &e);