fix attribute resolvers to ensure no expression is built if operators or values are missing, in that case, attribute presence/existence is checked using the 'hasAttribute()' method
fix attribute resolvers to ensure no expression is built if operators or values are missing, in that case, attribute presence/existence is checked using the 'hasAttribute()' method

dperini/nwmatcher,dperini/nwmatcher,dperini/nwmatcher