debug consistency: fix unused-but-set-variable warning #943

Job	Run time
CMake Serial Minimal Build on Linux	1m 14s
CMake Serial With Clawpack Build on Linux	9m 40s
CMake Serial With Clawpack and HDF Build on Linux	10m 32s
CMake Serial With GeoClaw Build on Linux	4m 5s
CMake Serial With CudaClaw (CUDA 10.1) Build on Linux	3m 14s
CMake Serial With CudaClaw (CUDA 11.3) Build on Linux	3m 37s
CMake MPI Minimal Build on Linux	2m 14s
CMake MPI With Clawpack Build on Linux	8m 33s
CMake MPI With Clawpack and HDF Build on Linux	10m 4s
CMake MPI With GeoClaw Build on Linux	4m 8s
CMake build on MacOS	7m 17s
CMake MPI With CudaClaw (CUDA 10.1) Build on Linux	3m 46s
CMake MPI With CudaClaw (CUDA 11.3) Build on Linux	4m 6s
CMake MPI With ThunderEgg Build on Linux	3m 57s
	1h 16m 27s

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