cubicweb-leaflet #5739655 fix icon definition for cases where marker_icon is None in adapters [validation pending]

fix icon definition for cases where marker_icon is None in adapters

and add backward (pre-0.4.2) compat of marker.icon

prioritynormal
typebug
done in0.4.3
load0.100
load left0.000
closed by#1152a7ea023d fix icon definition for cases where marker_icon is None in adapters
patchfix icon definition for cases where marker_icon is None in adapters [applied]