VOCemission receives negative cisun_z and cisha_z values

### Brief summary of bug

`cisun_z` and `cisha_z` are -999 for non-bareground pfts

### General bug information

**CTSM version you are using:** [output of `git describe`]

ctsm5.3.014-1-g51517197b
https://github.com/mvdebolskiy/CTSM/tree/bug/isoprene-check
just add this check in VOCemission, before the gamma_c is calculated:
```fortran
if (cisha_z(p,1) < 0.0_r8 .or. cisun_z(p,1) < 0.0_r8) then
write(iulog,*) 'Invalid intercellular co2 pressure (patch itype, sunlit, shaded): ', patch%itype(p),cisun_z(p,1),cisha_z(p,1)
call endrun(subgrid_index=p, subgrid_level=subgrid_level_patch, msg=errMsg(sourcefile, __LINE__))
endif
```
**Does this bug cause significantly incorrect results in the model's science?** [Yes / No]

No idea

**Configurations affected:** [Fill this in if known.]

At least `Clm60Sp` and `Clm60Bgc` compsets.

### Details of bug

`cisun_z` is set to -999 in the begining of the `clm_drv`, even though photosynthesis routines are called before `VOCemission`, not all the patches actually assign a proper value.

### Important details of your setup / configuration so we can reproduce the bug
These tests:
SMS_D_Lm3.f09_f09_mg17.I2000Clm60Sp.derecho_intel.clm-default
SMS_D_Lm3.f09_f09_mg17.I2000Clm60Bgc.derecho_intel.clm-default

### Important output or errors that show the problem