TypeError while scanning file (PDF)

### Description

When scanning a PDF from https://github.com/hopding/pdf-lib (rev 4beebbef7a261ed0be089bb1d63a5b6e28cc488a) we receive:

> TypeError while scanning file 'assets/pdfs/with_invalid_objects.pdf' (int() argument must be a string, a bytes-like object or a real number, not 'PSKeyword'

### How To Reproduce

ScanCode 32.1.0 via ORT (22.5.0)

```
config:
ScanCode:
options:
commandLine: "--copyright --license --license-text --info --strip-root --timeout\
\ 600"
parseLicenseExpressions: "true"
```

### System configuration

* What OS are you running on? (Windows/MacOS/Linux)
* Linux
* What version of scancode-toolkit was used to generate the scan file?
* 32.1.0
* What installation method was used to install/run scancode? (pip/source download/other)
* pip in ORT