Throw when despawning all entity of a world with relation involve

[warquys]

using var world = new World();
var parent = world.Spawn();
var otherParent = world.Spawn();

world.Spawn().Add(0, parent).Add(0, otherParent);
// Crash  VVVVVVV result in an new archetype will iterating over.
world.All.Despawn();

System.InvalidOperationException : Collection was modified after the enumerator was instantiated.
   at System.Collections.Generic.SortedSet`1.Enumerator.MoveNext()
   at fennecs.Query.Truncate(...) in Query.cs:line 415
   at fennecs.Query.Despawn() in Query.cs:line 387