since AssetHandle does not have a name_property
(RNA_def_struct_name_property), and the UIList is just using the
default uilist_filter_items_default it simply cannot filter on names
(RNA_struct_name_get_alloc wont succeed).
Adding a name_property also wont work since AssetHandle inherits
PropertyGroup (which already sets name_property).
So this adds a (temporary) hack exception for RNA_AssetHandle in
uilist_filter_items_default until the design of AssetHandle progresses
further.
thx @Julian Eisel (Severin) for additional feedback