Warning: Undefined array key "idUsuario" in C:\xampp\htdocs\decimo\sistema\includes.php on line 84

Fatal error: Uncaught PDOException: SQLSTATE[23000]: Integrity constraint violation: 1048 Column 'idUsuario' cannot be null in C:\xampp\htdocs\decimo\sistema\clases\sql.php:48 Stack trace: #0 C:\xampp\htdocs\decimo\sistema\clases\sql.php(48): PDOStatement->execute(Array) #1 C:\xampp\htdocs\decimo\sistema\clases\carrito.php(28): insertarOActualizar(Array, 'carrito') #2 C:\xampp\htdocs\decimo\sistema\includes.php(87): crearCarritoUsuario(NULL) #3 C:\xampp\htdocs\decimo\contacto.php(3): include('C:\\xampp\\htdocs...') #4 {main} thrown in C:\xampp\htdocs\decimo\sistema\clases\sql.php on line 48