Hardcoded assumption for number of NI instances in GOCART2G

[rmontuoro]

The GOCART2G grid component assumes that at least one instance of NI is present:

GOCART/ESMF/GOCART2G_GridComp/GOCART2G_GridCompMod.F90

Line 968 in e2245c2

if ((self%NI%instances(1)%is_active) .and. (index(self%NI%instances(1)%name, 'data') == 0 )) then ! Nitrates currently only support one active instance. We check the NI gridded component because SO4MASS can be altered by NI chemistry.

This will cause runtime failures in configurations without NI.

[bena-nasa]

@rmontuoro, thanks for bringing this up. Yes, I just opened another issue, related to this (#222). We need to be able to selectively turn off the GOCART2G components like was eminently doable in GOCART. This is one example of issues that prevent that.