Fix #1964 (Fix for Checkbox field)
Fix #1964 (Fix for Checkbox field)

lsaffre/lino_extjs6,lino-framework/extjs6,lsaffre/lino_extjs6,lsaffre/lino_extjs6,lino-framework/extjs6,lsaffre/lino_extjs6,lino-framework/extjs6,lsaffre/lino_extjs6