[FIX] Dropdown facets may provide empty values (no value is a value), skip them from the display as they cannot be queries anyway

git-svn-id: file:///var/local/code.tiki.org/tikisvn/trunk@46541 b456876b-0849-0410-b77d-98878d47e9d5
[FIX] Dropdown facets may provide empty values (no value is a value), skip them from the display as they cannot be queries anyway (part 2)

git-svn-id: file:///var/local/code.tiki.org/tikisvn/trunk@46542 b456876b-0849-0410-b77d-98878d47e9d5