make dock invisible on WIonWS

[Jian Fan]

Hi,

I'd like dock to disappear when I switch to WIonWS, and come back when I
switch to float workspace. Here's what I got so far:

ioncore.get_hook("region_activated_hook"):add(
    function(region) 
        if docktable then
            if obj_is(reg, "WIonWS")  then
                -- io.stderr:write("my hook is being run\n")
                mod_dock.set_floating_shown_on(WRegion.screen_of(region), 
'unset')
            else
                mod_dock.set_floating_shown_on(WRegion.screen_of(region), 'set')
        end
    end
end
)

I got:
/usr/local/bin/ion3: Attempt to call an unsafe function "set_floating_shown_on" 
in restricted mode

I found ioncore.defer() but wasn't able to get that working either. I
was also wondering if I'm on the right track since I'm quite new to Ion
and Lua. Thanks.

Jian