[BUG][EDITOR] Errors and leftovers regarding sets with no objects / no terrains

[namida]

Reported in IRC by Simon:

> The object / terrain selection often cannot be accessed if the level's primary graphic set has no pieces of the respective type, even though the piece selector now allows selecting from any set
> In cases where the menu can be accessed under such circumstances, it causes an error

Have not yet investigated and/or attempted to reproduce, will do so next time I'm working on the editor.

[namida]

@Simon:

I can reproduce the inability to access the menu (fixed for next update), but not the errors. How exactly did you trigger these?

[namida]

I was able to trigger an error by clicking "OK" while the currently selected graphic set is one without any pieces of the relevant type. This is fixed for the next update.

Was there any other ways you found to cause an error, or is this the only one?

[Simon]

I haven't seen errors besides (click OK in gadget picker with empty list). The main irritation was (gadget picker is disallowed altogether because there are no gadgets in the primary set).

I merely reported how the gadget picker was disallowed. Everything else is a side effect of discussion.

-- Simon

[namida]

Alright. Both of those two issues are fixed for next update.