Reverting class changes in commit window can cause signaling of a MessageNotUnderstood

[Rinzwind]

In a new image, after repairing the ‘pharo’ repository by cloning it again, and recalculating its dirty packages (through the menu item in the ‘Extra’ submenu in the context menu), committing shows various changes, and trying to revert the ones to ‘FileList class’, as shown on the following screenshot, causes a MessageNotUnderstood to be signaled (“#requirements was sent to nil”):

Tested using: Pharo 12 build 1491.

As for the issue of there being changes in a new image, see: issue #16238.