Fixed a seg fault when you try to use a CurlCurl integrator without supplying a coeff.
Fixed a seg fault when you try to use a CurlCurl integrator without supplying a coeff.

mfem/mfem,mfem/mfem,gelever/lamfem,mfem/mfem,mfem/mfem,kvoronin/mfem-4d-own,mfem/mfem