Missing Comments Restricting Drop-Down leads to JavaScript error

It is possible to adjust global and project specific permissions such that the drop-down to select comment restrictions is empty and thus not displayed.

This leads to a javascript error and the user is presented a popup saying:
"This page is asking you to confirm that you want to leave - data you have entered may not be saved. Leave Page Stay on Page" (FF 14/Linux)

The issue can be reproduced as follows:

• install standalone 5.1.1 x64 linux (as non-root)
• create a humble user with membership only in jira-users
• create a project and set its Users role to jira-developers
• adjust permission settings as follows:
  • Browse Issues: add jira-users
  • Add Comment: add jira-users
• create an issue in the created project
• login and add a comment with the humble user to the created issue
  => Dialog appears and user has to click 'Leave Page' to add the comment

Workaround:

• In Global Settings, switch Comment visibility from 'Project Roles only' to 'Groups & Project roles'

JavaScript error looks as follows in Chrome Developer Tools:

Uncaught TypeError: Cannot call method 'split' of undefined
commentForm.getCommentVisibility in jira.webresources:viewissue-components.js:70
commentForm.ajaxSubmit in jira.webresources:viewissue-components.js:70
commentDrawer.ajaxSubmit in jira.webresources:viewissue-components.js:70
$.delegate.delegate.delegate.delegate.delegate.delegate.delegate.delegate.delegate.delegate.bind.bind.bind.bind.preventEscClosingComments in jira.webresources:viewissue-components.js:70
f.event.dispatch in batch.js:3
f.event.add.h.handle.i in batch.js:3

Note that the behavior is not reproducible in a development environment (e.g. using atlas-run from a bare bone jira5 plugin directory)