[bfss] Fix update of BFSS attribute to None (close #1875289)
The current code assume attr value is alway a valide Binary value. But when the
attr is optional, the value might be None. The change handle this case.
[facets] make sure has_text facet data is posted correctly (closes #1857405)
Posted data was associated to facet id (e.g. has-text-123098dasdf898adssdd)
rather than facet name (i.e. has-text).