Fix memory leak in vtkMath::SolveLeastSquares.

This fix is in reference to issue #0002698. During the execution of method
vtkMath::SolveLeastSquares, if a matrix inversion failed then the method
would exit without dealocating locally allocated memory. This Fix corrects
this behavior.

Reviewed-by and Acked-by copied by hand due to a rebase.

Reviewed-by: @utkarsh.ayachit
Acked-by: @ben.boeckel
Acked-by: @robertmaynard