Addresses comments

Author: protocol86

FirebaseAuthUI/FUIAuth.m

@@ -235,7 +235,7 @@ - (void)signInWithProviderUI:(id<FUIAuthProvider>)providerUI
  originalError:error
  completion:^(FIRAuthDataResult *_Nullable authResult,
  NSError *_Nullable error,
- FIRAuthCredential *_Nullable credential) {
+ FIRAuthCredential *_Nullable existingCredential) {
  if (error) {
  completeSignInBlock(nil, error);
  return;
@@ -325,7 +325,9 @@ - (void)signInWithEmailHint:(NSString *)emailHint
  [self.auth fetchProvidersForEmail:emailHint completion:^(NSArray<NSString *> *_Nullable providers,
  NSError *_Nullable error) {
  if (error) {
- completion(nil, error, nil);
+ if (completion) {
+ completion(nil, error, nil);
+ }
  return;
  }
  NSString *existingFederatedProviderID = [self authProviderFromProviders:providers];
@@ -359,7 +361,7 @@ - (void)signInWithEmailHint:(NSString *)emailHint
  completion(nil, originalError, nil);
  }
  }];
- } else {
+ } else { // Federated sign-in case.
  id<FUIAuthProvider> authProviderUI;
  // Retrieve the FUIAuthProvider instance from FUIAuth for the existing provider ID.
  for (id<FUIAuthProvider> provider in self.providers) {
@@ -418,6 +420,9 @@ - (void)signInWithEmailHint:(NSString *)emailHint
  }
  }];
  }
+ if (completion) {
+ completion(authResult, error, credential);
+ }
  }];
  }];
  }