If you ever want to get a clean groups.txt file, delete your current one from garrysmod/data/ULib and then simply restart your server and ULib will build a new one.
Many people don't follow the instructions in Ulib addons group.txt (Though, many have trouble understanding it)
Never edit /addons/ULib/data/ulib/groups.txt
Never edit /addons/ULib/data/ulib/groups.txt
Never edit /addons/ULib/data/ulib/groups.txt
Never edit /addons/ULib/data/ulib/groups.txt

If you're going to make custom groups file,
ALWAYS create/edit a NEW <gmod root>/data/ULib/groups.txt (<--<<---- notice, there is no addons folder there)
ALWAYS create/edit a NEW <gmod root>/data/ULib/groups.txt (<--<<---- notice, there is no addons folder there)
ALWAYS create/edit a NEW <gmod root>/data/ULib/groups.txt (<--<<---- notice, there is no addons folder there)
ALWAYS create/edit a NEW <gmod root>/data/ULib/groups.txt (<--<<---- notice, there is no addons folder there)
Then when it totally breaks, you can follow Mr.Presidents instructions