[local_auth] Fix iOS app crash issue: alerts should be alled in the m…

packages/local_auth/CHANGELOG.md

@@ -1,8 +1,7 @@
-## 1.1.0
-
 * Migrate to null safety.
 * Allow pin, passcode, and pattern authentication with `authenticate` method.
 * Fix incorrect error handling switch case fallthrough.
+* Fix crash on biometric lockout
 * Update README for Android Integration.
 * Update the example app: remove the deprecated `RaisedButton` and `FlatButton` widgets.
 * Fix outdated links across a number of markdown files ([#3276](https://github.com/flutter/plugins/pull/3276)).

packages/local_auth/ios/Classes/FLTLocalAuthPlugin.m

@@ -69,9 +69,14 @@ - (void)alertMessage:(NSString *)message
                 }];
     [alert addAction:additionalAction];
   }
-  [[UIApplication sharedApplication].delegate.window.rootViewController presentViewController:alert
-                                                                                     animated:YES
-                                                                                   completion:nil];
+  @try {
+      dispatch_async(dispatch_get_main_queue(), ^{
+          [[UIApplication sharedApplication].delegate.window.rootViewController presentViewController:alert  animated:YES  completion:nil];
+      });
+  } @catch (NSException *exception) {
+      NSLog(@"Exception presentViewController: %@", exception);
+  } @finally {
+  }
 }
 
 - (void)getAvailableBiometrics:(FlutterResult)result {