Small change made previously to tensor_2nd_invariant subroutine making the test case work for 1D, 2D and 3D
Small change made previously to tensor_2nd_invariant subroutine making the test case work for 1D, 2D and 3D

rjferrier/fluidity,jrper/fluidity,jrper/fluidity,jjo31/ATHAM-Fluidity,iakovos-panourgias/fluidity,jrper/fluidity,jjo31/ATHAM-Fluidity,jjo31/ATHAM-Fluidity,rjferrier/fluidity,iakovos-panourgias/fluidity,jjo31/ATHAM-Fluidity,jrper/fluidity,jrper/fluidity,rjferrier/fluidity,iakovos-panourgias/fluidity,iakovos-panourgias/fluidity,iakovos-panourgias/fluidity,jjo31/ATHAM-Fluidity,rjferrier/fluidity,rjferrier/fluidity