fix: m_opt_backup_value not being initialized in CUICheckButton (#2049)

Co-authored-by: Xottab-DUTY <xottab-duty@yandex.ru>

Author: AMS21

src/xrUICore/Buttons/UICheckButton.h

@@ -34,7 +34,7 @@ class XRUICORE_API CUICheckButton final : public CUI3tButton, public CUIOptionsI
     pcstr GetDebugType() override { return "CUICheckButton"; }
 
 private:
-    bool m_opt_backup_value;
+    bool m_opt_backup_value{};
     void InitTexture2(LPCSTR texture_name);
     CUIWindow* m_pDependControl;
 };