Handle erroneously configured TreeView DynamicFields.

[svenoe]

Select Fields in TreeView do not work if sub categories are set without the base category being present.
(E.g. plant::tree and plant::bush being used without plant being used. This is not always the case - see ov71 for an example.)

The nicest way to handle this, would probably be to add the node dynamically but disable its selection. Else at least a useful error message should appear somewhere.

[stefanhaerter]

Besides the changes I already made, it seems to be necessary to alter the code in https://github.com/RotherOSS/otobo/blob/rel-10_1/Kernel/Output/HTML/Layout.pm#L5938 in the following way:

$Row->{Key} = '-'; to $Row->{Key} = substr $Row->{Key}, 0, (length($Row->{Key}) - length('_Disabled'));

because in Core.UI.TreeSelection.js the options are sorted alphabetically and the Key '-' causes the items to be displayed wrongly, as far as I see. However, I'm not entirely sure if the Key currently used is needed in any other place.

[stefanhaerter]

Closed with merging #2529