Dapp Browser does not handleReject correctly

[jessgusclark]

Describe the bug (required)
When using the Dapp browser, the user signs a transaction or message, and hits cancel, the handleReject function is fired. However, this error is not passed back to the sendAsync function.

In addition, the id property is not assigned or used. This may be the identifier that is used, although it is unclear. More investigation is required.

With PR #653 a hack was introduced to check if the response from RN is not undefined. If it is, it will throws a generic provider error.

App & Device (required)
N/A

To Reproduce
Steps to reproduce the behavior:

1. Go to the dapp browser tab
2. Log on to https://basic-sample.rlogin.identity.rifos.org/
3. Click 'Connect with rLogin'
4. Click 'Sign Message
5. Click 'Cancel'
6. Expected error message to be [ERROR]: User reject as shown here

Additional context
Add any other context about the problem here.

• References PR Improve dapp browser #653