fix two problems in the Dir module: #2069

Job	Run time
macos-aarch64	2m 17s
macos	3m 39s
x86_64_linux_native_builds (x86_64-unknown-linux-gnu)	23s
rust_stable	21s
solaris (x86_64-pc-solaris)	6m 23s
minver	17s
x86_64_linux_native_builds (x86_64-unknown-linux-musl)	27s
aarch64_linux_native_builds (aarch64-unknown-linux-musl)	29s
aarch64_linux_native_builds (aarch64-unknown-linux-gnu)	29s
tier3 (x86_64-unknown-haiku)	57s
rustfmt	9s
tier3 (x86_64-unknown-dragonfly)	1m 2s
tier3 (x86_64-unknown-openbsd)	1m 3s
tier3 (armv7-unknown-linux-uclibceabihf)	37s
cross	-1s
redox	-1s
cross_compiling	-1s
	18m 30s

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