Fixing some issues found by the linter

backend/internal/database/db.go

@@ -104,6 +104,9 @@ func (d *Db) Migrate(dirname string) error {
 		log.Println("Executed SQL file:", file.Name())
 	}
 
-	tr.Commit()
+	if tr.Commit() != nil {
+		return err
+	}
+
 	return nil
 }

backend/internal/database/db_test.go

@@ -36,7 +36,9 @@ func TestDbGetUserId(t *testing.T) {
 	if err != nil {
 		t.Error("setupState failed:", err)
 	}
-	db.AddUser("test", "password")
+	if db.AddUser("test", "password") != nil {
+		t.Error("AddUser failed")
+	}
 
 	var id int