It's a civil case, not criminal. You only need a perponderance of evidence and if you invoke the 5th it's perfectly legal to make an adverse inference against you.

How would lawsuits work if that wasn't possible? Civil lawyers aren't able to use as many powers in evidence gathering as prosecutors. If uber's current tactic was allowed then every company would hire a designated employee who would have a paper trail of all the company's misdoings lead to him. That employee then pleads the fifth, the company does a shrug, and that's the end of the lawsuit