build: prevent compile-time failure in application extensions

TIUIElements/Sources/Helpers/Extensions/UIViewController+FixedTopOffet.swift

@@ -11,7 +11,16 @@ public extension UIViewController {
         if #available(iOS 13.0, *) {
             statusBarHeight = window?.windowScene?.statusBarManager?.statusBarFrame.height ?? 0
         } else {
-            statusBarHeight = UIApplication.shared.statusBarFrame.height
+            // prevent compile-time failure: 'shared' is unavailable in application extensions for iOS
+
+            let sharedSelector = Selector(("shared"))
+
+            if UIApplication.responds(to: sharedSelector),
+               let sharedApplication = UIApplication.perform(sharedSelector).takeRetainedValue() as? UIApplication {
+                statusBarHeight = sharedApplication.statusBarFrame.height
+            } else { // application extension, statusBarFrame is not applicable
+                statusBarHeight = .zero
+            }
         }
 
         let navigationBarHeight = navigationBar?.bounds.height ?? 0