Bulk closing issues in a group throws an error

This applies to the latest version of GitLab.

To reproduce:

• Go to a group, not just an individual project. (Perhaps the group needs to also have subgroups.)
• In the left menu, go to Plans > Work Items
• The search bar will contain "State is Open". Add "Label is 'On Master'". I suppose you first need a label called "On Master".
• Press Enter to search. (I found 27 items).
• Click "Bulk Edit"
• Click the checkbox beside the search bar to select them all.
• On the view that pops in from the right, select "State Closed".
• Click "Update Selected".
• You get an error message that says, "Something went wrong while bulk editing."