[2.1.11] Spawners will not spawn defensive units

[KiNg626]

Spawners will not spawn any units that have join_attacks=false in their ai_settings. This is true both for the passive spawns up to the spawner unit cap, and when the spawner is receiving enough pollution to create an attack.

What did you do?
Changed the small biter prototype to have join_attacks=false in their ai_settings
What happened?
Biter spawner spawned nothing until evolution passed 0.2, at which point it spawned an unchanged medium biter.
What did you expect to happen instead?
The spawner should spawn small biters up to the defensive unit cap.
Does it happen always, once, or sometimes?
Always