chem: add scalar guards for p_hcl and p_ch3cl in add_anthropogenics t…

[AlphaBetaGammaChi]

Fixes a runtime SIGSEGV crash during emissions_driver when running chemical mechanisms that do not include anthropogenic chlorine (such as CRI-MECH with emiss_opt = 19 or emiss_opt = 20).

Cause
In chem/module_emissions_anthropogenics.F, assignments for p_hcl and p_ch3cl were placed in the generic anthropogenic emissions loop without param_first_scalar bounds checks.
For mechanisms where e_hcl and e_ch3cl are not present in the package, referencing chem(..., p_hcl) and emis_ant(..., p_e_hcl) causes an invalid memory reference and crashes on timestep 1:

Program received signal SIGSEGV: Segmentation fault - invalid memory reference.
Backtrace:
__module_emissions_driver_MOD_emissions_driver
chem_driver_
solve_interface_

[weiwangncar]

The regression results:

Test Type              | Expected  | Received |  Failed
= = = = = = = = = = = = = = = = = = = = = = = =  = = = =
Number of Tests        : 23           24
Number of Builds       : 60           57
Number of Simulations  : 158           150        0
Number of Comparisons  : 95           86        0

Failed Simulations are: 
None
Which comparisons are not bit-for-bit: 
None