Delete event on resource queued for eviction causes crash

[jirenius]

Issue

A delete event sent on a resource that exists in Resgate's cache, but is queued for eviction due to having 0 subscriptions, causes Resgate to crash.

How to reproduce

• Have a client subscribe a resource: subscribe.test.model
• Have the client unsubscribe the resource: unsubscribe.test.model
• Have the service send a delete event: event.test.model.delete

Impact

• No security impact
• Causes clients to be forced to resync once Resgate is restarted

[jirenius]

Resolved in #143