Improve user error handling.

object/token.go

@@ -179,7 +179,7 @@ func GetOAuthCode(userId string, clientId string, responseType string, redirectU
 	user := GetUser(userId)
 	if user == nil {
 		return &Code{
-			Message: "Invalid user_id",
+			Message: fmt.Sprintf("The user: %s doesn't exist", userId),
 			Code:    "",
 		}
 	}

object/user.go

@@ -313,6 +313,10 @@ func AddUser(user *User) bool {
 		user.Id = util.GenerateId()
 	}
 
+	if user.Owner == "" || user.Name == "" {
+		return false
+	}
+
 	organization := GetOrganizationByUser(user)
 	user.UpdateUserPassword(organization)