cubicweb #2587883 Facets crash if no title specified [validation pending]

Facets crash if no title specified

prioritynormal
typebug
done in3.17.3
load0.100
load left0.000
closed by#d42540bacff4 [facet] don't crash if no title specified on a facet and filtered rset is empty. Closes #2587883
patch[facet] prevent from crashing facet if no title specified (closes #2587883) [applied]