refactor: changed lifecycle callback to late

lib/src/lifecycle_event_handler.dart

@@ -3,28 +3,20 @@ import 'package:flutter/foundation.dart';
 
 class LifecycleEventHandler extends WidgetsBindingObserver {
   LifecycleEventHandler({
-    this.resumeCallBack,
-    this.suspendingCallBack,
+    required this.resumeCallBack,
   });
 
-  final AsyncCallback? resumeCallBack;
-  final AsyncCallback? suspendingCallBack;
+  late final AsyncCallback resumeCallBack;
 
   @override
   Future<void> didChangeAppLifecycleState(AppLifecycleState state) async {
     switch (state) {
       case AppLifecycleState.resumed:
-        if (resumeCallBack != null) {
-          await resumeCallBack!();
-        }
+        await resumeCallBack();
         break;
       case AppLifecycleState.inactive:
       case AppLifecycleState.paused:
       case AppLifecycleState.detached:
-        if (suspendingCallBack != null) {
-          await suspendingCallBack!();
-        }
-        break;
     }
   }
 }

lib/src/qr_code_scanner.dart

@@ -98,7 +98,6 @@ class _QRViewState extends State<QRView> {
               widget.key as GlobalKey<State<StatefulWidget>>, _channel,
               overlay: widget.overlay)
         });
-
     return false;
   }
 
@@ -139,7 +138,7 @@ class _QRViewState extends State<QRView> {
         break;
       default:
         throw UnsupportedError(
-            "Trying to use the default webview implementation for $defaultTargetPlatform but there isn't a default one");
+            "Trying to use the default qrview implementation for $defaultTargetPlatform but there isn't a default one");
     }
     return _platformQrView;
   }
@@ -199,7 +198,7 @@ class QRViewController {
           }
           break;
         case 'onPermissionSet':
-          await getSystemFeatures(); // if we have no permission all features will not be avaible
+          await getSystemFeatures(); // if we have no permission all features will not be available
           if (call.arguments != null) {
             if (call.arguments as bool) {
               _hasPermissions = true;