ActorCell.DeathWatch InvalidOperationException during AddressTerminated

[Aaronontheweb]

Had the following exception occur here: https://github.com/akkadotnet/akka.net/blob/dev/src/core/Akka/Actor/ActorCell.DeathWatch.cs#L213

Exception:

System.InvalidOperationException occurred
_HResult=-2146233079
_message=Collection was modified; enumeration operation may not execute.
HResult=-2146233079
IsTransient=false
Message=Collection was modified; enumeration operation may not execute.
Source=System.Core
StackTrace:
at System.Collections.Generic.HashSet`1.Enumerator.MoveNext()
InnerException:

Looks like loop modifies _state.GetWatchedBy()'s underlying collection while it iterates.