StorageManager#loadModel will invoke an error callback if the result set is empty and never trigger any loaded shenanigans.
StorageManager#_handleNextLayer's arguments is an object, just like #_loadCollectionWithFirstLayer
Error handler gets passed when doing additional server requests
Merge pull request #13 from mavenlink/bugfix_load_model_empty

StorageManager#loadModel and #_handleNextLayer with error callbacks