MPC causes segfault on Frontier

**Describe the bug**

Use of MPC is unstable on Frontier (CPU code). A handful of FeCl2 runs have segfaulted, one run has produced NaN.

**To Reproduce**

Build details:
```
Git branch: develop
Last git commit: 283f2438770bdfb592d161d287771764cbf6f96c
Last git commit date: Sat Aug 26 09:36:21 2023 -0500
Last git commit subject: Merge pull request #4715 from QMCPACK/prckent-patch-1

Currently Loaded Modules:
1) craype-x86-trento 13) darshan-runtime/3.4.0
2) libfabric/1.15.2.0 14) hsi/default
3) craype-network-ofi 15) DefApps/default
4) perftools-base/22.12.0 16) emacs/28.1
5) xpmem/2.6.2-2.5_2.22__gd067c3f.shasta 17) cmake/3.23.2
6) cray-pmi/6.1.8 18) openblas/0.3.17
7) cce/15.0.0 19) cray-fftw/3.3.10.3
8) craype/2.7.19 20) hdf5/1.14.0
9) cray-dsmml/0.2.2 21) boost/1.79.0
10) cray-mpich/8.1.23 22) rocm/5.5.1
11) cray-libsci/22.12.1.1 23) ninja/1.10.2
12) PrgEnv-cray/8.3.3

Executable:
/lustre/orion/world-shared/mat151/pk7/try_frontier/build_frontier_cpu_real_MP/bin/qmcpack
```

Problem cases (segfault):
```
FeCl2-tile-3-hyb-0-spo-0-est-0-walk-180/qmc.out:srun: error: frontier04992: task 7: Segmentation fault (core dumped)
FeCl2-tile-3-hyb-0-spo-0-est-0-walk-1024/qmc.out:srun: error: frontier08960: task 4: Segmentation fault (core dumped)
FeCl2-tile-3-hyb-0-spo-0-est-0-walk-1680/qmc.out:srun: error: frontier10366: task 6: Segmentation fault (core dumped)
FeCl2-tile-3-hyb-0-spo-0-est-0-walk-2400/qmc.out:srun: error: frontier00384: task 5: Segmentation fault (core dumped)
FeCl2-tile-3-hyb-0-spo-0-est-0-walk-3360/qmc.out:srun: error: frontier08319: task 3: Segmentation fault (core dumped)
FeCl2-tile-3-hyb-0-spo-0-est-0-walk-3840/qmc.out:srun: error: frontier00208: task 6: Segmentation fault (core dumped)
FeCl2-tile-4-hyb-0-spo-0-est-0-walk-720/qmc.out:srun: error: frontier00201: task 0: Segmentation fault (core dumped)
```

Problem case (NaN in scalar.dat):
`FeCl2-tile-2-hyb-0-spo-0-est-0-walk-1680`

Location on Frontier:
`/lustre/orion/mat151/proj-shared/ecp_vdw_test_runs/frontier_files/test_runs_jk_cpu/runs_2023-09-11-09-15-23`

To reproduce, copy the relevant files in a new directory and resubmit (`sbatch qmc.sbatch.in`).

**Expected behavior**
No segfaults or NaN's