201 slack - i keep getting an error that says "the browser is closed"

### Issue Details

i am unable to continue editing the slack webhook app. i keep getting this error after authorizing slack:


i've tried adding a new connection as well. i can't continue.
### Repro steps (_if necessary, delete otherwise_)
1. deploy the template
2. click edit
3. try to authorize slack

NOTE: the app was successfully authorized in slack - i got an email

Start by deploying the template and reproducing the Slack authorization flow described in the issue. Check the browser-closed error after authorization; it is done when a successfully authorized Slack connection allows editing to continue without that error.

Written by the indexing model from the issue text.