Build

Replace NULL with nullptr #536

Job	Run time
ubuntu (22.04)	6m 49s
ubuntu (24.04)	7m 31s
macOS (latest, 3.9, 5.9.*, release)	6m 34s
windows (win64_msvc2017_64, 3.6, x64, 5.11.*)	4m 34s
windows (win32_mingw53, 3.6, x86, 5.11.*)	6m 4s
oldschool (rockylinux, 9, release)	4m 14s
windows (win64_msvc2019_64, 3.13, x64, 5.15.*, PythonQtCore PythonQtGui PythonQtMultimedia)	3m 45s
oldschool (rockylinux, 9, debug)	3m 49s
macOS (latest, 3.9, 5.9.*, debug)	8m 9s
windows (win64_mingw73, 3.10, 5.12.*, x64)	5m 33s
macOS (latest, 3.11, 5.12.*, debug)	3m 13s
	1h 0m 15s

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