I've merged a fix, which will go into the next release. There should be a 7.9.2 release in the next 1-2 weeks.
If you would like to test it sooner, it's possible but requires building apm-server yourself:
- install Make and Go 1.13.10
- clone https://github.com/elastic/apm-server/tree/7.9
- run
make release TYPES=docker - run
docker image load -i build/distributions/apm-server-7.9.2-linux-amd64.docker.tar.gz