There's a PHP fatal error in PHP 7.2 when count() is not a countable object or array, like when it's null.
This issue can exist for https://github.com/easydigitaldownloads/easy-digital-downloads/blob/c91cfd9cd984c856b345f88fa9fc0b00887a737c/includes/emails/class-edd-email-tags.php#L211
I just ran into this today, while testing on 7.2. Plausible there are other places this is needed, but it's hard to sniff them out until there are tests/problems.
Put into the 3.0 milestone for now. If we encounter this more, we can move to a point release if necessary.
All unit tests that use count() need to be updated as well - PHP 7.2 changed the way the count() method is used: https://wiki.php.net/rfc/counting_non_countables.
Currently we have 61 unit tests failing on PHP 7.2 with the same error as above - I'll go ahead and open a PR with so that our test matrix can also test against PHP 7.2 as it was released as of 30 November 2017.
Core build now passes with PHP 7.2
Closing this out as the build currently passes with no issues when tested against PHP 7.2.