Check this field is set first

[specialtactics]

I was updating some VCR files, and I noticed we had this problem occur:

ErrorException: Undefined index: request_header

/var/www/vendor/allejo/php-vcr-sanitizer/src/VCRCleanerEventSubscriber.php:199
/var/www/vendor/allejo/php-vcr-sanitizer/src/VCRCleanerEventSubscriber.php:58
/var/www/vendor/symfony/event-dispatcher/EventDispatcher.php:230
/var/www/vendor/symfony/event-dispatcher/EventDispatcher.php:59
/var/www/vendor/php-vcr/php-vcr/src/VCR/Videorecorder.php:106

It may be related to the fact that we updated all packages very recently.

So I had a look, and making the change in this PR fixed the issue for us. I also did a dump of the curl info in $workspace to make sure it is actually set in general, and everything else looked fine.

[allejo]

Thanks @specialtactics! I've tagged v1.0.8 with this patch 😄