test/test_svg: don't fail if we don't have any classes on an element #1190

Job	Run time
valgrind	45s
build-and-dist (gcc)	51s
build-and-dist (gcc, -Db_sanitize=address,undefined -Db_lundef=false)	34s
build-and-dist (clang)	54s
build-and-dist (clang, -Db_sanitize=address,undefined -Db_lundef=false)	35s
duplicate-devices	21s
etcdir (sudo mv /usr/share/libwacom/wacom-intuos*.tablet /etc/libwacom)	23s
clean-svg-check	29s
etcdir (sudo mv /usr/share/libwacom/*.tablet /etc/libwacom)	26s
build-from-tarball	59s
etcdir (sudo mv /usr/share/libwacom/*.stylus /etc/libwacom)	25s
etcdir (sudo mv /usr/share/libwacom/*.tablet $HOME/.config/libwacom)	28s
etcdir (sudo mv /usr/share/libwacom/*.stylus $HOME/.config/libwacom)	26s
etcdir (sudo mv /usr/share/libwacom/wacom-*.tablet $HOME/.config/libwacom && sudo mv /usr/share/l...	34s
etcdir (sudo csplit data/wacom.stylus '/^\[0x822\]/' && sudo mv xx00 /etc/libwacom/first.stylus &...	24s
	8m 34s

Provide feedback