PHP Warning module purchase

### Environment

```Markdown
- PHP: 8.4.16
- MySQL: 11.4.9-MariaDB
```

### Current Behavior

PHP Warning:  Undefined array key "" in /home/server/public_html/modules/purchase/index.php on line 25

### Expected Behavior

_No response_

### Steps To Reproduce

.

### Anything else?

_No response_