title: nonnull value as return value in method doesn't work?
body: <p>I thought that if I specified <code>nonnull</code> attribute for the return value in method, and try to return nil/null - app will crash, but I see that app didn't crashed, it successful returned null. It's expected behaviour (Nullability is just for compatibility with Swift, and no real help for ObjC code, or I'm doing something wrong?
  My method declaration that returning me null:</p>
  
  <pre><code>- (nonnull PFObject *)getParseObjFromManagObj:(nonnull NSManagedObject *)managObj;
  </code></pre>