Below a stack trace we've been seeing a couple of times lately in our
wxSqueak project (which is mostly 3.8). It seems that SuspendedDelays
has a nil element somewhere. However, the code in Delay seems to be
safe against that and I can't see any code elsewhere in the image that
messes around with delays...

Has anyone ever seen this?

UndefinedObject(Object)>>doesNotUnderstand: #resumptionTime
[] in Delay class>>DoIt {[:t2 :t3 | t2 resumptionTime <= t3 resumptionTime]}
SortedCollection>>indexForInserting:
SortedCollection>>add:
[] in Delay>>schedule {[beingWaitedOn := true.  resumptionTime := Time
millisecondClockValue + dela...]}
[] in Semaphore>>critical: {[t2 := t1 value]}
BlockContext>>ensure:
Semaphore>>critical:
Delay>>schedule
Delay>>wait
TUDispatchingDatagramChannel(TUDatagramChannel)>>retransmissionRun
[] in TUDispatchingDatagramChannel(TUDatagramChannel)>>start {[self
retransmissionRun]}
BlockContext>>repeat
[] in TUDispatchingDatagramChannel(TUDatagramChannel)>>start {[[self
retransmissionRun] repeat]}
[] in BlockContext>>newProcess {[self value.  Processor terminateActive]}