Issues CSV export fails when given an issue where `author` is nil

I'm not sure if this is due to the size of the export, or a particular issue tripping things up.

I couldn't see anything in sentry

It could also be Sidekiq MemoryKiller , but I can't see memory usage going near 1GB on Grafana - Sidekiq Workers (ExportCsvWorker). Although I believe SIDEKIQ_MEMORY_KILLER_MAX_RSS is set to 1000000ckb, the graph could be excluding shared memory.