Fix error handling in script

[kristianfreeman]

When a selector lookup or something similar fails inside of the code (see https://github.com/totemprotocol/roam-backup/runs/496115224?check_suite_focus=true#step:5:17 for an example), the script is catching the error and making it so that the workflow step returns as successful.

https://github.com/signalnerve/roam-backup/blob/master/index.js#L108

[Stvad]

have provisional fix for this in my fork