AND-79 Fix WC crash loop

[Radiokot]

Purpose

Fix a crash loop caused by a malformed WalletConnect verifiable presentation request

Changes

• Check WC ID proof request nullability
• Handle unexpected WC session request handling errors
• Await the WC connection before sending responses

Checklist

• My code follows the style of this project.
• The code compiles without warnings.
• I have performed a self-review of the changes.
• I have documented my code, in particular the intent of the
  hard-to-understand areas.
• (If necessary) I have updated the CHANGELOG.