[BUGFIX beta] Fixes issue - class given as unconditional binding to view not applied.

Passing `classBinding` to `view` helper is broken.  
When the context for the view is an arrayController and it's content is empty then  the class which is given unconditional, is not applied..   
Failing bin: http://emberjs.jsbin.com/yokej/2/edit  

Working bin in 1.5.0: http://emberjs.jsbin.com/vikuza/1/edit  

This PR addresses it.

cc: @rwjblue
@mixonic Sounds reasonable. Will change.