Default local initSelection returns the actual selected items

Fix for issue #934. The default initSelection uses a matcher to find
items that match the selection, but if the data is hierarchical what
the matcher returns may actually be grouping elements, so they can't be
treated as a list of matching items.  This fix runs the matcher but
rather than using its return value it collects the matching item(s)
into a closure-scoped variable and then returns that.