If you delete all ssh keys in the textarea then LuCI will rais an error.
So if you added one ssh-key to the textarea and then you want to delete them
again that is not possbile in LuCI.
To fix this remove "rmempty" attribute and add a remove function which will
called if the textarea is empty.
Signed-off-by: Florian Eckert <fe@dev.tdt.de>
0251603f0a