Relation editor closes on ESC without asking for confirmation

[Bernhard Hiller <bhil@…>]

The relations editor can be closed by pressing ESC (Version 4279). It does not ask for a confirmation, even when the relation was edited. Thus some work can get lost.
Background: I edited some cycle routes. While the relations editor was opened, I edited some ways (divide them, correct the position of nodes, add nodes, even add complete ways); for getting rid of the editing mode for ways, I use the ESC key. Sometimes the relation editor happened to have the focus and was closed...
A simple confirmation message box for closing the editor on ESC (when the relation is "dirty") should be added, e.g.
"You are about to close the relations editor without saving. All your changes to the relation will be lost. Are you sure?"
Yes: close without saving
No: save the changes, and close the editor
Cancel: do not close the editor