Don't show the 'view layout' button for input sources that are not keyboard layouts

If you have the 'Japanese (Kana Kanji)' input method enabled (this probably also applies to other input methods), then it is shown in the list under 'Input Sources' on the 'Region & Language' applet. Next to it are shown three buttons: a cog for 'settings', an X for 'remove', and an eyeball, which is intended to show you a visual representation of the keyboard layout (that's what you get if you click the eyeball for any entry that is a keyboard layout).

Showing the eyeball here is kind of wrong, because an input method is not a keyboard layout and you can't really provide a 'visual representation' of it. If you click the eyeball, it seems that it tries to run gkbd-keyboard-display -l with a value that is not a keyboard layout, and that crashes - the crash is reported as libgnomekbd#1 , but even if that crash is fixed, I think showing the button here at all for input methods is wrong, so filing this separately.