[mainUI] No way to delete explicitly set value in an add-on configuration

[dilyanpalauzov]

Using openHAB 5.1.0 build 4923 I install the BasicUI add on and under Settings → Add-on Settings I set a default sitemap. When I visit GET …/basicui/app the system does not ask me to select the sitemap to display.

Now I change my mind and want that the system asks me, which sitemap to display. Under Add-on Settings → Basic UI → Default Sitemap I delete the value and click on Save. When I reload the BasicUI settings, the old value for the default sitemap is still displayed, whatever I do. The only way to force BasicUi to ask me which sitemap to display is to enter here as value of an non-existent sitemap.

• When an addon configuration value is deleted in MainUI and the configuration is saved, that value must be deleted from the filesystem.