Add error handling to handlers of VC message

[ibuibu]

What

Expanded implimentation of error handling added in this PR to the handlers of VC Message. https://github.com/nodecross/nodex/pull/281

Check

1. generate vc message by example code.
2. delete vc message from DB.
3. verify vc message by example code.
4. the result is below.

❯ python verify_vc_message.py                                   
Now Requesting...
- Method: POST
- URL: http+unix:///Users/hirokiibuka/.nodex/run/nodex.sock:/verify-verifiable-message

The response is as follows.

404 Not Found "Message Activity ID not found"