tests

fix minor bugs in treeSeqMetadata() #1396

Job	Run time
tests-Unix-GUI (ubuntu-20.04, 5.9.5, 7)	5m 32s
tests-Unix-CLI (ubuntu-20.04, 7, 3.8)	5m 55s
tests-Unix-GUI (ubuntu-20.04, 5.15.2, 11)	7m 12s
tests-Windows-CLI (mingw64, x86_64, 3.8)	17m 44s
canceller	6s
tests-Unix-CLI (ubuntu-20.04, 11, 3.9)	7m 28s
tests-Unix-GUI (ubuntu-22.04, 5.15.2, 12)	6m 56s
tests-Windows-CLI (ucrt64, ucrt-x86_64, 3.8)	18m 14s
tests-Unix-CLI (macos-13, 3.9)	13m 52s
tests-Unix-GUI (ubuntu-22.04, 6.7.2, 12)	7m 35s
tests-Windows-GUI (mingw64, x86_64)	13m 9s
tests-Unix-GUI (macos-13, 5.15.2)	12m 8s
tests-Unix-CLI (macos-15, 3.9)	5m 0s
tests-Windows-GUI (ucrt64, ucrt-x86_64)	12m 47s
tests-windows-latest-pacman (mingw64, x86_64)	1m 29s
tests-Unix-GUI (macos-15, 6.7.2)	4m 44s
tests-windows-latest-pacman (ucrt64, ucrt-x86_64)	1m 32s
	2h 21m 23s

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