Debugger Service panic on "Step Forward" outside oplog range

[andrueandersoncs]

On my branch of the Golem Console, I'm attempting to use the debugger service to Step Forward to a given oplog entry index.

Debugging with @mschuwalow this morning, we discovered that a panic happens in the following situation:

1. Connect a debugging session for a given agent
2. Invoke the agent via invoke-and-await HTTP API (I did this x3)
3. Select an oplog index (outside the debugging session's oplog range) -> Step Forward
4. Observe panic (terminal session hosting the services crashes entirely)