[PHP 8.0] ArgumentCountError: Too few arguments to function MigrationBase::errorHandler(), 4 passed and exactly 5 expected in MigrationBase->errorHandler()

Problem/Motivation

When using this module with PHP 8.0, if the PHP error handler gets called, you'll get this error:

ArgumentCountError: Too few arguments to function MigrationBase::errorHandler(), 4 passed and exactly 5 expected in MigrationBase->errorHandler()

This is due to the $context argument being removed in PHP 8.0:

https://www.php.net/manual/en/function.set-error-handler#refsect1-functi...

Steps to reproduce

Use this module and get an error. :-)

Proposed resolution

I'll attach a patch in a moment that will work with both PHP 7 and 8.0

Remaining tasks

1. Make patch
2. Review
3. Commit!

User interface changes

None

API changes

Adding a default to the 5th argument of MigrationBase::errorHandler()

Data model changes

None