Do not require where clause in condition on queries.

[nlutsenko]

This is not required for $select, so looks like it shouldn't be required for $dontSelect.
Fixes parse-community/Parse-SDK-iOS-OSX#845

[codecov-io]

Current coverage is 91.30%

Merging #925 into master will increase coverage by +0.28% as of b74e49e

@@            master   #925   diff @@
=====================================
  Files           72     72       
  Stmts         4166   4301   +135
  Branches       862    862       
  Methods          0      0       
=====================================
+ Hit           3792   3927   +135
  Partial         10     10       
  Missed         364    364       

Review entire Coverage Diff as of b74e49e

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