applets/kicker: two fixes to custom icon configuration
Kicker's configuration page has a somewhat complex handling of the custom icon, which is spread across three properties. When the custom icon is cleared, the property that governs which of the other properties is used is set. but the actual icon is not cleared. This means that setting and resetting the icon will still prompt the user to save the changes to the (now unused) property. This would be meaningful if the custom icon could be reactivated, but the only way to enable it again is to set it again, at which point the stored value would be overwritten anyway.
Instead, remove the value of the custom property as well if the icon is cleared.
Kicker's custom icon button handles the icon dialog's iconName property being changed, and stores the result in its own configuration. This will fail sometimes: if the user sets a custom icon, clears it using the icon button's "Clear Icon" function, and sets the same custom icon again, the icon will not be changed as the icon dialog's property is unchanged by selecting the same icon again.
Instead, we listen to the icon dialog's accepted signal, and only set the custom icon if an icon was actually chosen.
Second commit requires frameworks/kiconthemes!179 (merged)