More verbose comments in FIRIAMClientInfoFetcher, call completion in case that FIS token is fetched, but FID fails

Author: christibbs

FirebaseInAppMessaging/Sources/Flows/FIRIAMClientInfoFetcher.m

@@ -51,6 +51,7 @@ - (void)fetchFirebaseInstallationDataWithProjectNumber:(NSString *)projectNumber
             if (error) {
               FIRLogWarning(kFIRLoggerInAppMessaging, @"I-IAM190008", @"Error in fetching FID: %@",
                             error.localizedDescription);
+              completion(nil, tokenResult.authToken, error);
             } else {
               FIRLogDebug(kFIRLoggerInAppMessaging, @"I-IAM190009",
                           @"Successfully in fetching both FID as %@ and FIS token as %@",

FirebaseInAppMessaging/Sources/Private/Analytics/FIRIAMClientInfoFetcher.h

@@ -21,8 +21,9 @@
 
 NS_ASSUME_NONNULL_BEGIN
 @interface FIRIAMClientInfoFetcher : NSObject
-// Fetch the up-to-date FID and FIS token data. Since it involves a server interaction,
-// completion callback is provided for receiving the result.
+// Fetch the up-to-date Firebase Installation ID (FID) and Firebase Installation Service (FIS) token
+// data. Since it involves a server interaction, completion callback is provided for receiving the
+// result.
 - (void)fetchFirebaseInstallationDataWithProjectNumber:(NSString *)projectNumber
                                         withCompletion:
                                             (void (^)(NSString *_Nullable FID,