Fixed night mode.

android/src/main/kotlin/net/touchcapture/qr/flutterqr/QRView.kt

@@ -39,31 +39,31 @@ class QRView(private val registrar: PluginRegistry.Registrar, id: Int) :
         channel.setMethodCallHandler(this)
         checkAndRequestPermission(null)
         registrar.activity().application.registerActivityLifecycleCallbacks(object : Application.ActivityLifecycleCallbacks {
-            override fun onActivityPaused(p0: Activity?) {
+            override fun onActivityPaused(p0: Activity) {
                 if (p0 == registrar.activity()) {
                     barcodeView?.pause()
                 }
             }
 
-            override fun onActivityResumed(p0: Activity?) {
+            override fun onActivityResumed(p0: Activity) {
                 if (p0 == registrar.activity()) {
                     barcodeView?.resume()
                 }
             }
 
-            override fun onActivityStarted(p0: Activity?) {
+            override fun onActivityStarted(p0: Activity) {
             }
 
-            override fun onActivityDestroyed(p0: Activity?) {
+            override fun onActivityDestroyed(p0: Activity) {
             }
 
-            override fun onActivitySaveInstanceState(p0: Activity?, p1: Bundle?) {
+            override fun onActivitySaveInstanceState(p0: Activity, p1: Bundle) {
             }
 
-            override fun onActivityStopped(p0: Activity?) {
+            override fun onActivityStopped(p0: Activity) {
             }
 
-            override fun onActivityCreated(p0: Activity?, p1: Bundle?) {
+            override fun onActivityCreated(p0: Activity, p1: Bundle?) {
             }
         })
     }