bug fix rename leaving dangling specifications

The asset manager finishes processing changes by iterating the
specifications object.  There is working code to remove components if a
layer name was ‘player.png’ and is now just ‘player’, but leaving empty
arrays out of the specifications object prevented it from running
Merge pull request #269 from adobe-photoshop/jhatwich/layer-update

fix layer rename leaving dangling specifications
Merge branch 'master' into jhatwich/layerComps+size