Compilation failure using mingw32 when -Wconversion is enabled. #7597

Job	Run time
mingw (mingw64)	3m 45s
build (windows-2019, Win32, v142, 17, Debug)	1m 15s
build (windows-2019, Win32, v142, 17, Release)	2m 33s
mingw (ucrt64)	4m 11s
build (windows-2019, Win32, v142, 17, -DBUILD_SHARED_LIBS=ON, Debug)	1m 29s
build (windows-2019, Win32, v142, 17, -DBUILD_SHARED_LIBS=ON, Release)	2m 11s
build (windows-2019, x64, v141, 14, Debug)	1m 22s
build (windows-2019, x64, v141, 14, Release)	2m 9s
build (windows-2019, x64, v141, 17, Debug)	1m 19s
build (windows-2019, x64, v141, 17, Release)	2m 14s
build (windows-2019, x64, v142, 17, Debug)	1m 49s
build (windows-2019, x64, v142, 17, Release)	2m 52s
build (windows-2019, x64, v142, 17, -DBUILD_SHARED_LIBS=ON, Debug)	1m 59s
build (windows-2019, x64, v142, 17, -DBUILD_SHARED_LIBS=ON, Release)	2m 53s
build (windows-2019, x64, v142, 20, Debug)	1m 51s
build (windows-2019, x64, v142, 20, Release)	2m 52s
build (windows-2022, x64, v143, Debug, 20)	1m 50s
	38m 34s

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