Fixes narrowing conversion #489

Job	Run time
B2 gcc-11	3m 39s
B2 msvc-14.2	5m 47s
B2 clang-14	3m 56s
CMake msvc-14.2 Debug C++17	8m 19s
B2 msvc-14.3	6m 4s
CMake gcc-11 17 Debug	8m 39s
CMake msvc-14.2 Release C++17	8m 16s
CMake msvc-14.3 Debug C++20	10m 28s
CMake gcc-11 20 Release	11m 2s
CMake clang-11 17 Debug	6m 15s
CMake msvc-14.3 Release C++20	9m 38s
CMake clang-11 20 Debug	6m 45s
CMake clang-13 17 Release	8m 56s
CMake clang-13 20 Release	9m 39s
CMake clang-14 17 Debug -stdlib=libc++	8m 36s
CMake clang-14 20 Release -stdlib=libc++	11m 30s
	2h 7m 29s

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