Validation not working when attributes contain property length

[juneidy]

I have done some debugging and it is due to _.each prioritising array. Reference: jashkenas/underscore#2407

[juneidy]

To make it easy for you, it happens in the function flatten in backbone-validation-amd.js

[jekuno]

For details also see this issue: https://github.com/gmac/backbone.epoxy/issues/124