Fix crash from force-unwrap on orphaned PumpEventStored with nil bolus

This commit removes a force-unwrap from our pump event pipeline and
replaces it with more idiomatic swift optional handling. The net
effect of a pump event of type `bolus` that doesn't have a
corresponding `bolus` property is that it'll show up in the history UI
as a blank bolus but these events will be filtered out of the pump
history before passing them to the algorithm.

Without this fix, when one of these pump events sneaks into an
individual's pump history it will cause their app to crash before
doing anything, so they have to either wait 24 hours for the pump
event to age out or delete trio and start over. With the fix, it will
filter these events out in a way that is consistent with the existing
code for pump event handling.

Trio/Sources/APS/Storage/PumpHistoryStorage.swift

@@ -291,13 +291,16 @@ final class BasePumpHistoryStorage: PumpHistoryStorage, Injectable {
     }
 
     func determineBolusEventType(for event: PumpEventStored) -> PumpEventStored.EventType {
-        if event.bolus!.isSMB {
+        guard let bolus = event.bolus else {
+            return event.type.flatMap({ PumpEventStored.EventType(rawValue: $0) }) ?? .bolus
+        }
+        if bolus.isSMB {
             return .smb
         }
-        if event.bolus!.isExternal {
+        if bolus.isExternal {
             return .isExternal
         }
-        return PumpEventStored.EventType(rawValue: event.type!) ?? PumpEventStored.EventType.bolus
+        return event.type.flatMap({ PumpEventStored.EventType(rawValue: $0) }) ?? .bolus
     }
 
     func getPumpHistoryNotYetUploadedToNightscout() async throws -> [NightscoutTreatment] {