fix(ast): correct (in)equality operators against null operands
fix(ast): correct (in)equality operators against null operands

aurelia/binding,JeroenVinke/binding,jdanyow/binding,bigopon/binding,davismj/binding,jods4/binding,cmichaelgraham/binding,mbroadst/binding,z-brooks/binding,shanonvl/aurelia-binding,hitesh97/binding