[Bug] Constructing the Hydrogel functional with a grade argument results in error

[joshichaitanya3]

The Hydrogel functional allows a number grade as an optional argument, but the construction fails with a HydrglArgs error.

To Reproduce Run the following code in the test/functionals/hydrogel directory:

var m0 = Mesh("tetrahedron.mesh")
var lh = Hydrogel(m0, grade=2)

[softmattertheory]

Is this still a problem @joshichaitanya3 ?