UAParser\Parser::parse() must be of the type string, null given

**Describe the bug**
Whenever I try to do anything, including starting the server locally, I get:

In Parser.php line 35:
Argument 1 passed to UAParser\Parser::parse() must be of the type string, null given, called in D
:\Projects\*****\vendor\pragmarx\tracker\src\Support\UserAgentParser.php on line 25

Removing the package, obviously, removes the error. But nothing else I have done (reinstall, clear cache, add package to non-discover, etc) has worked.
This literally started overnight with no configuration changes or packages updated, so I'm at a loss as to what to do. Any help would be greatly appreciated.

**System**
- Laravel: 5.8.*
- antonioribeiro /tracker: 3.5.0

Start by reproducing the error while running Laravel 5.8 with antonioribeiro/tracker 3.5.0. Read Parser.php line 35 and vendor/pragmarx/tracker/src/Support/UserAgentParser.php line 25 to trace the null argument. Done means identifying the triggering condition and confirming that starting the server and normal tracker use no longer produce the type error.

Written by the indexing model from the issue text.