When you try in messaging, provider setting of some provider, in journal tab set some numeric attribute (attributes : journal-buffer-size, journal-min-files ...) to zero, the change is not propagated to model and after refreshing page the previous value is shown.
Setting value to zero through CLI works right.

Edit:
Also is problem when you change attribute to some valid value and save, after reload of server the previous value is shown. - problem is only with default server

But when you set value of journal numeric attribute and save it and then try to undefine the attribute through web console, it doesn't work.