Cancel button confirmation message for unsaved IPE changes doesn't appear after new panes are added

If you have unsaved changes in the IPE and then click the cancel button, a confirmation message is supposed to pop up that says "This will discard all unsaved changes. Are you sure?".

This message correctly appears when you've rearranged or deleted existing panes. However, if you add a new pane during an IPE editing session (but have not rearranged or deleted any existing ones), the message does not appear. It should, because your new pane will disappear after the Cancel button is clicked.