Fix FPEs occurring when density is zero in MC #19598

Job	Run time
Commits	8s
Clang-tidy (Debug)	9m 31s
Files and formatting	5m 58s
Clang-tidy (Release)	8m 32s
Archs (gcc-9)	27m 36s
Unit tests (gcc-9, Debug)	24m 23s
Unit tests on macOS (x86, 13, 4)	1h 14m 2s
Unit tests (gcc-9, Release)	15m 22s
Archs (gcc-10)	38m 5s
Unit tests on macOS (arm64, 14, 3)	12m 28s
Unit tests (gcc-10, Debug)	25m 12s
Unit tests (gcc-10, Release)	16m 13s
Archs (clang-13)	36m 21s
Unit tests (gcc-11, Debug)	25m 29s
Archs (clang-14)	44m 30s
Unit tests (gcc-11, Release)	11m 28s
Unit tests (clang-13, Release, OFF, OFF, JEMALLOC)	13m 16s
Unit tests (clang-13, Debug, OFF, OFF, normal)	12m 2s
Unit tests (clang-14, Debug, ON, OFF, JEMALLOC, 2)	31m 24s
Unit tests (clang-14, Release, 3.18.2, /work/charm_7_0_0/mpi-linux-x86_64-smp-clang, 3, ON, ON)	16m 29s
Documentation	8m 12s
Deploy documentation	0s
Release version	0s
	7h 36m 41s

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