curses ui: fix default color detection #665

Job	Run time
build (ubuntu-latest)	2m 28s
build (ubuntu-latest, --disable-curses)	2m 29s
build (ubuntu-latest, --disable-lua)	2m 15s
build (ubuntu-latest, --disable-tre)	3m 16s
build (ubuntu-latest, --disable-selinux)	2m 26s
build (ubuntu-latest, --disable-acl)	2m 35s
build (ubuntu-latest, --disable-help)	2m 22s
build (ubuntu-20.04)	2m 45s
build (ubuntu-20.04, --disable-curses)	2m 50s
build (ubuntu-20.04, --disable-lua)	2m 31s
build (ubuntu-20.04, --disable-tre)	2m 48s
build (ubuntu-20.04, --disable-selinux)	3m 36s
build (ubuntu-20.04, --disable-acl)	2m 54s
build (ubuntu-20.04, --disable-help)	2m 46s
	38m 1s

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