CarpetX: output invalid array indices in debug mode #1416

Job	Run time
download-build-test (cpu, real32, debug)	10m 31s
download-build-test (cpu, real64, debug)	10m 37s
download-build-test (cpu, real64, optimize)	17m 15s
download-build-test (cuda, real32, debug)	21m 29s
download-build-test (cuda, real64, debug)	21m 45s
download-build-test (cuda, real64, optimize)	21m 29s
download-build-test (rocm, real64, optimize)	20m 1s
download-build-test (oneapi, real64, optimize)	27m 28s
	2h 30m 35s

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