Fix isAuthenticated in CognitoAuth caused by scopes unmarshalling (#874)

* [CognitoAuth] Fix string to set logic that caused isAuthenticated to return false #809

* Update CHANGELOG.md

Author: minbi

.idea/modules.xml

@@ -15,6 +15,9 @@
 * **AWS Mobile Client**
   * Fixed a bug that caused repetitive sign-in using the drop-in UI to the same provider to not federate the correct credentials. See [issue #809](https://github.com/aws-amplify/aws-sdk-android/issues/809)
 
+* **Amazon Cognito Auth**
+  * Fixed a bug that caused `isAuthenticated()` to return false after sign-in when no scopes were requested. See [issue #813](https://github.com/aws-amplify/aws-sdk-android/issues/813)
+
 * **Amazon Pinpoint**
   * Fix a bug where the image that is part of a push notification is persisted in the subsequent notifications.
   * Fix a bug where the events recorded and stored in the device will not be deleted when the network is not available. See [issue #773](https://github.com/aws-amplify/aws-sdk-android/issues/773). With this change, the events will be kept in the local database when there is a retryable error or device is offline. For all other exceptions during `submitEvents`, the exception is logged and the events will be removed from the local database.

CHANGELOG.md

@@ -26,6 +26,7 @@
 import com.amazonaws.mobileconnectors.cognitoauth.tokens.IdToken;
 import com.amazonaws.mobileconnectors.cognitoauth.tokens.RefreshToken;
 import com.amazonaws.mobileconnectors.cognitoauth.AuthUserSession;
+import com.amazonaws.util.StringUtils;
 
 import java.security.InvalidParameterException;
 import java.util.Arrays;
@@ -504,7 +505,12 @@ static String setToString(Set<String> stringSet) {
     }
 
     static Set<String> setFromString(String str) {
+        final HashSet<String> stringSet = new HashSet<>();
+        if (StringUtils.isBlank(str)) {
+            return stringSet;
+        }
         String[] stringArray = str.split(",");
-        return new HashSet<String>(Arrays.asList(stringArray));
+        stringSet.addAll(Arrays.asList(stringArray));
+        return stringSet;
     }
 }