InvalidOperationException: Collection was modified; enumeration operation may not execute.
StackTrace:
   at System.ThrowHelper.ThrowInvalidOperationException(ExceptionResource resource)
   at System.Collections.Generic.List`1.Enumerator.MoveNextRare()
   at System.Linq.Enumerable.<SkipIterator>d__31`1.MoveNext()
   at System.Linq.Enumerable.WhereSelectEnumerableIterator`2.MoveNext()
   at System.Collections.Generic.List`1..ctor(IEnumerable`1 collection)
   at System.Linq.Enumerable.ToList[TSource](IEnumerable`1 source)
   at BetterClip.Service.Windows.ActiveWindowService.<.ctor>b__6_3(EventPattern`1 _)
   at System.Reactive.AnonymousSafeObserver`1.OnNext(T value)
   at System.Reactive.Linq.ObservableImpl.Where`1.Predicate._.OnNext(TSource value)
   at System.Reactive.Linq.ObservableImpl.Throttle`1._.Propagate(UInt64 currentid)
   at System.Reactive.Concurrency.Scheduler.Invoke[TState](ValueTuple`2 tuple)
   at System.Reactive.Concurrency.Scheduler.<>c__78`1.<ScheduleAction>b__78_0(IScheduler _, ValueTuple`2 tuple)
   at System.Reactive.Concurrency.UserWorkItem`1.Run()
   at System.Reactive.Concurrency.ConcurrencyAbstractionLayerImpl.Timer.Tick()
   at System.Threading.ExecutionContext.RunInternal(ExecutionContext executionContext, ContextCallback callback, Object state, Boolean preserveSyncCtx)
   at System.Threading.ExecutionContext.Run(ExecutionContext executionContext, ContextCallback callback, Object state, Boolean preserveSyncCtx)
   at System.Threading.TimerQueueTimer.CallCallback()
   at System.Threading.TimerQueueTimer.Fire()
   at System.Threading.TimerQueue.FireNextTimers()