Steps to Reproduce
1 - Go to kb_knowledge.list
2 - Choose any knowledge article
3 - Right click choose configure > all
4 - Disable all the UI Policies
5 - Create a new UI Policy
6 - Create a new UI Policy Action that makes the wiki field mandatory
7 - Save
8 - Go to any knowledge article
Cannot read property 'removeClassName' of undefined
kb_knowledge.do:90 +-- Parse times
After carefully considering the severity and frequency of the issue, and the cost and risk of attempting a fix, it has been decided to not address this issue in any current or near future releases. We do not make this decision lightly, and we apologise for any inconvenience.
As a workaround, use a Client Script instead of a UI Policy.
Related Problem: PRB629137