Non-valid token format produces an unhandled error

[ozanyurtsever]

Describe the bug
When the format of the token string supplied is not a valid JWT, the decoded string is not parsable.

To Reproduce
Steps to reproduce the behavior:

1. Supply the necessary keys and ids from Cognito user pool
2. Run the verify function with suplying a non-valid token string(e.g; kskfma123231)
3. You will see an error: SyntaxError: Unexpected token � in JSON at position 0

Expected behavior
The error should be handled and a clear prompt should be given to the user.