Filter by 0 relations

[mhwelander]

https://prisma-company.slack.com/archives/C5Z9TH6N9/p1602854686016200

[nikolasburk]

Just adding this link for some public context for what this is issue is about as well: prisma/prisma#3888

[mhwelander]

Documented: https://www.prisma.io/docs/concepts/components/prisma-client/relation-queries#filter-on-presence-of-related-records