fix check issues for forthcoming updates #710

Job	Run time
R-CMD-check / macOS-latest (release)	33m 31s
R-CMD-check / windows-latest (devel)	35m 45s
R-CMD-check / windows-latest (release)	34m 54s
R-CMD-check / windows-latest (oldrel)	33m 38s
R-CMD-check / windows-latest (4.1)	2m 47s
R-CMD-check / ubuntu-latest (devel)	40m 4s
R-CMD-check / ubuntu-latest (release)	32m 30s
R-CMD-check / ubuntu-latest (4.3)	10m 16s
R-CMD-check / ubuntu-latest (4.2)	1m 6s
R-CMD-check / ubuntu-latest (4.1)	54s
R-CMD-check / ubuntu-latest (4.0)	57s
R-CMD-check / ubuntu-latest (3.6)	1m 6s
	3h 47m 28s

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