Custom Filter Widget: UX: a blank value must get the filter ignored for all query types

• Type: Bug
• Status: Open
• Resolution: Unresolved
• Affects Version/s: Master
• Fix Version/s: None
• Component/s: Search Infrastructure, Web Search > Search Widgets
• Labels: None
• Epic Link: Search Page and Widgets 7.3

UX is inconsistent when filter value is left blank. The intuitive experience is that a blank value would leave the filter out of the current search. With some query types, this already works. But with several others, a blank value leads to zero search results. This is actually a back end issue: infrastructure for complex query building should be checking for the blank value on all query types. At the front end, this should be accompanied by a "Clear" link consistent with the UX we already have in Facet Widgets.