Accept Blue payment handler should return Declined instead of throwing

[mschipperheyn]

Which plugin/repository is the issue about?
accept-blue

Describe the bug
The accept blue payment handler can throw an error in the handlePaymentForOrder method. That error should imho be caught in the payment handler in order to return a Declined state.

Expected behavior
Declined state with message supporting the reason

Screenshots
If applicable, add screenshots to help explain your problem.

Environment

• NodeJS version
• Vendure version: [e.g. 1.7.1] 2.2.x
• Plugin version [e.g. 3.1.1] 1.6.1