Possible to create a non-invertible affine or projective matrix with SubsetOf::to_superset

I was trying to figure out how to construct an `Affine2` that included a non-uniform scale, and I think I found an unintended route to be able to create a non-invertible affine transform that panics when inverted:

```rust
use simba::scalar::SubsetOf;

let s: Affine2 = Scale2::new(0.0, 0.0).to_superset();
s.inverse(); // panics since anything with `0` scale is non-invertable
```