Error trying to save 2d PFT outputs at landunit level when not gridded

### Brief summary of bug

I get an error when trying to save 2d PFT history outputs at landunit level with `hist_dov2xy = .false.`.

### General bug information

**CTSM version you are using:** ctsm5.4.038

**Does this bug cause significantly incorrect results in the model's science?** No

**Configurations affected:** See above.

### Details of bug

I tested the following combinations factorially in a 3-day simulation with annual history timesteps (i.e., I only checked for errors in initialization). The above (in **bold** here) is the only one that caused a problem.
- `hist_type1d_pertape`: PFTS, COLS, **LAND**, and GRID
- `hist_dov2xy`: true, **false**
- 1d vars (`GPP`, `GRAINC_TO_FOOD`) and **2d vars (`SDATES`, `GRAINC_TO_FOOD_PERHARV`, `GRAINC_TO_FOOD_ANN`)**

### Important details of your setup / configuration so we can reproduce the bug

- Compset: `IHistClm60BgcCropCrujra`
- Resolution: `f10_f10_mg37`

### Important output or errors that show the problem

Debug false:
```
forrtl: severe (174): SIGSEGV, segmentation fault occurred
Image PC Routine Line Source
libc.so.6 000014CF17BA5900 Unknown Unknown Unknown
. 00000000011EAE6A Unknown Unknown Unknown
cesm.exe 00000000006F8A4C p2l_2d 457 subgridAveMod.F90
```

Debug true:
```
forrtl: severe (408): fort: (2): Subscript #1 of the array SCALE_P2C has value 76 which is greater than the upper bound of 75

Image PC Routine Line Source
cesm.exe 0000000000D7DA3A p2l_2d 448 subgridAveMod.F90
cesm.exe 0000000000B619C0 hist_update_hbuf_ 1912 histFileMod.F90
cesm.exe 0000000000B4481E hist_update_hbuf 1392 histFileMod.F90
cesm.exe 000000000092C0E8 clm_drv 1485 clm_driver.F90
cesm.exe 000000000086BED4 modeladvance 913 lnd_comp_nuopc.F90
```