error creating customer credit note: Undefined index: sales_gl_code

On Customer Credit Note Entry if Customer Branch's tax is fully exempt then this error will fire:

Undefined index: sales_gl_code in file: C:\xampp\htdocs\world244\sales\includes\db\sales_credit_db.inc at line 156

solution: initialize this index in line 164 of file tax_calc.inc

$ret_tax_array['exempt'] = array('Value'=>0, 'Net'=>0, 'rate' => null, 'tax_type_id' => '', 'sales_gl_code' => '');