If a loader display name has the wrong number of colons, it uses the parent extension twice

If a group sql query has a:b:c:d as a group name and a:b:d as the display name, it will set the display name to be something like a:b:b:d. This works for one group (although it's very confusing in the UI), but fails on the second group because it has the same parent stem display name. The loader should just immediately fail if there is at least one colon and they don't match.