fix: don't try to advance time by Zero

[Jasper-M]

Correct me if that's impossible, but I suspect this caused some requirement failed errors to randomly occur in our CI.

[djspiewak]

Huh. This situation really should be impossible, simply because tick() should be vacuuming up everything which is available at the current time epoch, so the next should always be strictly greater than zero. If you're seeing cases where that isn't true, then something else is definitely broken.

[Jasper-M]

Huh, that does seem impossible indeed 🫤
Unfortunately as it only seems to occur sometimes, I didn't yet manage to get more information out of it than this stacktrace

java.lang.IllegalArgumentException: requirement failed
  at scala.Predef$.require(Predef.scala:324)
  at executeEmbed @ com.example.MySpec$$anon$1.<init>(MySpec.scala:46)
  at executeEmbed @ com.example.MySpec$$anon$1.<init>(MySpec.scala:46)

where 46 is the line where I call unsafeRunSync().

I have to admit that we are calling an actual database in this test in combination with TestControl, which I've suspected from the beginning is causing this issue. But still weird that it doesn't fail consistently in that case. And I don't see which other require call it can be.