Simplify not-null-or-undefined check
Merge pull request #988 from joliss/null-checks

Simplify not-null-or-undefined check
Remove deprecated metaPath reliance

Ember.metaPath is no longer used anywhere in Ember and
will almost certainly be deprecated in this PR

https://github.com/emberjs/ember.js/pull/2710
Merge pull request #989 from machty/remove-meta-path

Remove deprecated metaPath reliance