fix(firebase_auth): Update APN token once auth plugin has been initialized on iOS. (#8201)

Co-authored-by: Mike Diarmid <mike.diarmid@gmail.com>

Author: russellwheatley

packages/firebase_auth/firebase_auth/ios/Classes/FLTFirebaseAuthPlugin.m

@@ -59,6 +59,7 @@ @implementation FLTFirebaseAuthPlugin {
   NSObject<FlutterBinaryMessenger> *_binaryMessenger;
   NSMutableDictionary<NSString *, FlutterEventChannel *> *_eventChannels;
   NSMutableDictionary<NSString *, NSObject<FlutterStreamHandler> *> *_streamHandlers;
+  NSData *_apnsToken;
 }
 
 #pragma mark - FlutterPlugin
@@ -155,6 +156,8 @@ - (void)handleMethodCall:(FlutterMethodCall *)call result:(FlutterResult)flutter
   FLTFirebaseMethodCallResult *methodCallResult =
       [FLTFirebaseMethodCallResult createWithSuccess:successBlock andErrorBlock:errorBlock];
 
+  [self ensureAPNSTokenSetting];
+
   if ([@"Auth#registerIdTokenListener" isEqualToString:call.method]) {
     [self registerIdTokenListener:call.arguments withMethodCallResult:methodCallResult];
   } else if ([@"Auth#registerAuthStateListener" isEqualToString:call.method]) {
@@ -242,7 +245,7 @@ - (BOOL)application:(UIApplication *)application
 
 - (void)application:(UIApplication *)application
     didRegisterForRemoteNotificationsWithDeviceToken:(NSData *)deviceToken {
-  [[FIRAuth auth] setAPNSToken:deviceToken type:FIRAuthAPNSTokenTypeUnknown];
+  _apnsToken = deviceToken;
 }
 
 - (BOOL)application:(UIApplication *)app openURL:(NSURL *)url options:(NSDictionary *)options {
@@ -1285,4 +1288,16 @@ + (NSMutableDictionary *)getNSDictionaryFromUser:(FIRUser *)user {
   return userData;
 }
 
+- (void)ensureAPNSTokenSetting {
+#if !TARGET_OS_OSX
+  FIRApp *defaultApp = [FIRApp defaultApp];
+  if (defaultApp) {
+    if ([FIRAuth auth].APNSToken == nil && _apnsToken != nil) {
+      [[FIRAuth auth] setAPNSToken:_apnsToken type:FIRAuthAPNSTokenTypeUnknown];
+      _apnsToken = nil;
+    }
+  }
+#endif
+}
+
 @end