edit lists in update author whitelist will cause application crash

Expected behavior

I just installed the steem-fossbot-voter to heroku according to the instructions in the link:
https://github.com/Steem-FOSSbot/steem-fossbot-voter/blob/master/docs/installation.md

All look good and I went to dashboard to update author whitelist:

The application will crash and here is the log:
2018-04-30T04:18:20.501254+00:00 app[web.1]: npm ERR! This is probably not a problem with npm. There is likely additional logging output above.
2018-04-30T04:18:20.510288+00:00 app[web.1]:
2018-04-30T04:18:20.510651+00:00 app[web.1]: npm ERR! A complete log of this run can be found in:
2018-04-30T04:18:20.510993+00:00 app[web.1]: npm ERR! /app/.npm/_logs/2018-04-30T04_18_20_503Z-debug.log
2018-04-30T04:18:20.571937+00:00 heroku[web.1]: Process exited with status 1
2018-04-30T04:18:20.488413+00:00 heroku[router]: at=error code=H13 desc="Connection closed without response" method=GET path="/edit-algo?author_whitelist=bitcoinparadise+cizzo" host=chenlocus-steem-voter-bot.herokuapp.com request_id=ee984234-9723-489d-8c11-39fbe1a4b78d fwd="203.19.128.30" dyno=web.1 connect=1ms service=101ms status=503 bytes=0 protocol=https
2018-04-30T04:18:20.594857+00:00 heroku[web.1]: State changed from up to crashed

Actual behavior

Write here the details of the behaviour that you are experiencing as a bug.

I expect the application running well and update my whitelist.

How to reproduce

Write here every possible detail to reproduce the bug.

As I described above, install the Steem-FOSSbot to heroku app according to the instruction and then go to dashboard to set whitelist, here is an overview of the dashboard:
https://github.com/Steem-FOSSbot/steem-fossbot-voter/blob/master/docs/dashboard-overview.md

After input the names of whitelist, I pressed the 'update author whitelist' button, then the application crashed.

• Browser: chrome
• Operating system:windows 8