Panic instead of a Result<,>

[JorisDeRidder]

varpro sometimes panics instead of returning a Result, which makes it less suitable for "production" code. The underlying reason is a panic of the SVD module in nalgebra library that varpro uses under the hood. This module panics when there is a NaN among the singular values. I created an issue at the nalgbra Github repository #1475, and a kind developer already implemented a fix. There seems to be some delay in accepting his/her pull request, though. As soon as nalgebra implements this fix, I would like to request that varpro uses this new nalgebra version and catch the Result when the fit goes wrong.