Javascript Error in popup using backbone

Hello,

I am a developer at WPMU DEV using WPMU Dev Hustle and I noticed that most of the BackBone JS libs being used are old and there are afew JS error that occur when I set the ninja forms shortcode in a pop up as per this screenshot I noticed the error is mainly at the code where form validation is being set up and will only appear once I comment out the line in the JS that throws that error in Ninja Forms.
Kindly assist in debugging this or in a way around this since most users integrating Ninja forms into the Hustle Popups cannot.

Warm Regards
Paul Kevin