Fix component pool entity removal

ecs/physics_system.odin

@@ -1,10 +1,15 @@
 package ecs 
 
+import "core:log"
+
 PhysicsSystem :: struct {
    using base: SystemBase,
 }
 
 physics_system_update :: proc(physics_system: ^PhysicsSystem, coordinator: ^Coordinator, dt: f32) {
+    entities_to_delete := make([dynamic]EntityID)
+    defer delete(entities_to_delete)
+
     for entity in physics_system.entities {
         rigid_body := coordinator_get_component(RigidBodyComponent, coordinator, entity)
         transform := coordinator_get_component(TransformComponent, coordinator, entity)
@@ -12,5 +17,13 @@ physics_system_update :: proc(physics_system: ^PhysicsSystem, coordinator: ^Coor
 
         transform.position += rigid_body.velocity * dt
         rigid_body.velocity += gravity.force * dt
+
+        if transform.position.y < -15 {
+            append(&entities_to_delete, entity)
+        }
+    }
+
+    for entity in entities_to_delete {
+        coordinator_destroy_entity(coordinator, entity)
     }
 }