replaced iOs popup by throwing a flutter error

ios/Classes/BarcodeScanPlugin.m

@@ -27,7 +27,11 @@
 }
 
 - (void)barcodeScannerViewController:(BarcodeScannerViewController *)controller didScanBarcodeWithResult:(NSString *)result {
-    if (self.result) {
+    if (self.result && [result isEqualToString: @"PERMISSION_NOT_GRANTED"]){
+        self.result([FlutterError errorWithCode:@"PERMISSION_NOT_GRANTED"
+                                   message:nil
+                                   details:nil]);
+    } else if (self.result) {
         self.result(result);
     }
 }

ios/Classes/BarcodeScannerViewController.m

@@ -38,7 +38,8 @@
         if (success) {
             [self startScan];
         } else {
-            [self showNoCameraAccessAlert];
+          [self.delegate barcodeScannerViewController:self didScanBarcodeWithResult:@"PERMISSION_NOT_GRANTED"];
+          [self dismissViewControllerAnimated:NO completion:nil];
         }
     }];
 }
@@ -81,16 +82,6 @@
     }
 }
 
-- (void)showNoCameraAccessAlert {
-    UIAlertController *alertController = [UIAlertController alertControllerWithTitle:@"Camera access denied"
-                                                                             message:@"Camera access has been disabled for this application. To turn camera access back on, please go to the iOS settings application."
-                                                                      preferredStyle:UIAlertControllerStyleAlert];
-    [alertController addAction:[UIAlertAction actionWithTitle:@"OK" style:UIAlertActionStyleDefault handler:^(UIAlertAction *action) {
-        [self dismissViewControllerAnimated:YES completion:nil];
-    }]];
-    [self presentViewController:alertController animated:YES completion:nil];
-}
-
 - (void)toggle {
     [self toggleFlash:!self.isFlashOn];
     [self updateFlashButton];