findAndCount returning NaN for count

[followben]

Describe the bug
When using findAndCount on Postgres with a filterQuery that includes inverse relations, count can incorrectly return NaN

To Reproduce
Steps to reproduce the behavior:

1. check out https://github.com/followben/mikro-orm/tree/gh858
2. run yarn test GH858

Expected behavior
Count returns a number greater than or equal to zero (or findAndCount() throws an error).

Versions

Dependency	Version
node	12.x
typescript	3.9.7
mikro-orm	4.0.5
pg	8.3.0

[B4nan]

Add a reproduction

[followben]

Hah, you're too quick... I was upping one with the GH issue number attached.

[B4nan]

Good, ty :]

Anyway, I never merge those "repro PRs", the idea was that this "single file repro" should be part of the issue - I will be the one adding it to the codebase together with a fix.

[followben]

Why is that @B4nan? I mean, why aren't test cases worthy of merging?

[B4nan]

Why would I merge something that will cause build failures?

[followben]

Because someone went to the trouble of creating it as per the contribution guidelines. You can push to the PR to fix, correct?