Fix PHP Notice leading to an empty Result

Your workflow always returned no results for me. Running the provided PHP script in the Terminal manually showed, that the result contained, besides the XML Result, PHP Notice messages, e.g.:

```
Notice: Trying to get property of non-object in /Users/[...]/leoparser.php on line 35
<?xml version="1.0"?>
<items>[...]
```

This pull requests fixes this PHP Notice.

Thanks for the workflow