This addition makes sure that CS%ebt_struct is filled/computed if the user specifies
KHTH_USE_EBT_STRUCT = True.

Before this addition, an array for CS%ebt_struct got allocated and initialized to 0, if
KHTH_USE_EBT_STRUCT = True. But this array never got filled (with values other than 0)
unless the user selected any of the following options too:
1) KHTH_USE_FGNV_STREAMFUNCTION = True
2) USE_MEKE = True
3) KhTr_passivity_coeff > 0
4) MLE_front_length > 0
5) Output the diagnostic Rd_dx
6) Use resolution scaling for the a) Laplacian viscosity, b) interface height diffusivity,
c) tracer diffusivity, OR d) the MEKE viscosity contribution.