Fix tests failing (#36)

Reviewed-on: #36

backend/db.go

@@ -49,11 +49,8 @@ func (db *Db) GetUsers() ([]User, error) {
 func (db *Db) GetUser(id int) (*UserWithAllowance, error) {
 	user := &UserWithAllowance{}
 
-	err := db.db.Query("select u.id, u.name, sum(h.amount) from users u join history h on h.user_id = u.id where u.id = ?").
+	err := db.db.Query("select u.id, u.name, (select ifnull(sum(h.amount), 0) from history h where h.user_id = u.id) from users u where u.id = ?").
 		Bind(id).ScanSingle(&user.ID, &user.Name, &user.Allowance)
-	if errors.Is(err, mysqlite.ErrNoRows) {
-		return nil, nil
-	}
 	if err != nil {
 		return nil, err
 	}