Fix null error in jshint grunt plugin
Fix null error in jshint grunt plugin

An issue was filed on jshint's github about this
https://github.com/jshint/jshint/issues/2922. The solution seems to be to
explicitly define a reporterOutput option with a value of empty string.

After making this change, grunt builds ran flawlessly.

iFixit/pulldasher,iFixit/pulldasher,iFixit/pulldasher,iFixit/pulldasher