* Removing sessionToken and authData from _User objects included in a query
This bug caused sessionToken to be replaced on client side to some old
sessionToken from DB.
* Removing dangling variable that is never used
* Checking if object has defined key for Pointer constraints in liveQuery
If there is a liveQuery subscription, with Pointer type constrains (e.g
query.equalTo('user', Parse.User.current())), and new object has
undefined value for that field, we get this error:
error: Uncaught internal server error. [TypeError: Cannot read
property 'className' of undefined] TypeError: Cannot read property
'className' of undefined
at matchesKeyConstraints
(…/node_modules/parse-server/lib/LiveQuery/QueryTools.js:145:51)
