fix display of ARRAY fields inside of structure data types.

Previously ARRAY fields in structures were displayed, for example,
like 'ARRAY [1..2] OF ARRAY' instead of 'ARRAY [1..2] OF INT'. Because
of this error the array type can be really edited.

fix Traceback if search icon on library panel is clicked, when no
category/item is selected in the library.

The problem is here, that if nothing is selected method GetSelection()
returns root item, that doesn't have any python data associated with it.
This issue seems to be wx3.0 specified, because it doesn't exist
with wx2.8 on Windows.