Fix error management on user creation.

server/add_user.go

@@ -187,11 +187,12 @@ func (s *server) addUserHandler(w http.ResponseWriter, r *http.Request) {
 		if !errors.Is(err, ldap.ErrNotFound) {
 			log.Println("Can't create user ", name, ": already exists")
 			response.execute("exists")
+			return
 		} else {
+			// ErrNotFound (user doesn't exist): Here it's not an error, we can create user.
 			log.Println("Error getting user: ", err)
 			s.errorHandler(w, r)
 		}
-		return
 	}
 
 	err = s.ldap.AddGroup(name, "")