test/test_svg: don't fail if we don't have any classes on an element #1189

Job	Run time
valgrind	34s
build-and-dist (gcc)	53s
build-and-dist (gcc, -Db_sanitize=address,undefined -Db_lundef=false)	38s
build-and-dist (clang)	49s
build-and-dist (clang, -Db_sanitize=address,undefined -Db_lundef=false)	34s
clean-svg-check	32s
build-from-tarball	33s
duplicate-devices	29s
etcdir (sudo mv /usr/share/libwacom/wacom-intuos*.tablet /etc/libwacom)	1m 15s
etcdir (sudo mv /usr/share/libwacom/*.tablet /etc/libwacom)	27s
etcdir (sudo mv /usr/share/libwacom/*.stylus /etc/libwacom)	30s
etcdir (sudo mv /usr/share/libwacom/*.tablet $HOME/.config/libwacom)	27s
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...	24s
etcdir (sudo csplit data/wacom.stylus '/^\[0x822\]/' && sudo mv xx00 /etc/libwacom/first.stylus &...	55s
	9m 26s

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