fix(page): fix AddPage not checking if the template actually existed.

internal/database/svgdb.go

@@ -15,6 +15,7 @@ const GETSPECIFICSVGSQL string = "SELECT * FROM svg WHERE id = ?;"
 const GETSVGSQL string = "SELECT * FROM svg;"
 const DELETESVGSQL string = "DELETE FROM svg WHERE id = ?;"
 const RENAMESVGSQL string = "UPDATE svg SET name = ? WHERE id = ?;"
+const EXISTSSVGSQL string = "SELECT COUNT(*) FROM svg WHERE id = ?;"
 
 func InsertSVG(data *svg.TemplateData) error {
 	if _, err := database.Exec(INSERTSVGSQL, data.Id, data.Name); err != nil {
@@ -93,3 +94,15 @@ func RenameSvg(id string, name string) error {
 	}
 	return nil
 }
+
+func Exists(id string) (bool, error) {
+	res := database.QueryRow(EXISTSSVGSQL, id)
+
+	var count int
+
+	if err := res.Scan(&count); err != nil {
+		return false, err
+	}
+
+	return count > 0, nil
+}