test: do not allow empty Layout= lines #1180

Job	Run time
valgrind	30s
build-and-dist (gcc)	1m 32s
build-and-dist (gcc, -Db_sanitize=address,undefined -Db_lundef=false)	59s
build-and-dist (clang)	49s
build-and-dist (clang, -Db_sanitize=address,undefined -Db_lundef=false)	34s
clean-svg-check	33s
duplicate-devices	22s
build-from-tarball	1m 8s
etcdir (sudo mv /usr/share/libwacom/wacom-intuos*.tablet /etc/libwacom)	25s
etcdir (sudo mv /usr/share/libwacom/*.tablet /etc/libwacom)	1m 40s
etcdir (sudo mv /usr/share/libwacom/*.stylus /etc/libwacom)	28s
etcdir (sudo mv /usr/share/libwacom/*.tablet $HOME/.config/libwacom)	20s
etcdir (sudo mv /usr/share/libwacom/*.stylus $HOME/.config/libwacom)	27s
etcdir (sudo mv /usr/share/libwacom/wacom-*.tablet $HOME/.config/libwacom && sudo mv /usr/share/l...	52s
etcdir (sudo csplit data/wacom.stylus '/^\[0x822\]/' && sudo mv xx00 /etc/libwacom/first.stylus &...	21s
	11m 0s

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