check for existing transactionPath in execHandler

[mikec]

tryFindTransactionPath was sometimes being called after sendTransaction resolved, which would clear ctx.transactionPath causing the reporter output ctx.transactionPath[0].description to fail

fixes this error I was getting in the reporter output (after successful transaction) using the aragon dao acl create command:

Sending transaction [started]
→ Waiting for transaction to be mined...
Sending transaction [completed]
 ✖ Cannot read property 'description' of undefined

Seemed like the lowest impact fix .. but might be better to clean up the promise code to avoid a race condition like this

[stale]

This pull request has been automatically marked as stale because it has not had recent activity. It will be closed if no further activity occurs. Thank you for contributing to Aragon! 🦅

[sohkai]

Please keep this open 😄

[stale]

This pull request has been automatically marked as stale because it has not had recent activity. It will be closed if no further activity occurs. Thank you for contributing to Aragon! 🦅