Thanks for providing a hint for solving this issue. I am running PHP 7.0.25 so I did not test on PHP 7.2.
Please update to "1.2.19: Fixes error "count() Parameter must be an array or an object that implements Countable" to get the fix.
There may still be issues due to the included library so if you still run into "count($x)" issues please post back here and consider doing a PR at the recurr library. ( https://github.com/simshaun/recurr/ )
This file for example has multiple uses of "count()":