POSITION SET EARLIEST fails on empty ring

[crotwell]

THis is probably a rare condition, but for a empty, new ringserver, a client sending this is ok and will start getting data once it begins flowing:

MATCH FDSN:CO_.*
STREAM

but this fails with ERROR: Error positioning reader:

MATCH FDSN:CO_.*
POSITION SET EARLIEST
STREAM

Seems like POSITION SET EARLIEST should cause no harm even on an empty ring.

Use case is that you want to start the consumer immediately after starting ring which may be before the producer has sent any data.

Similar issue for POSITION SET LATEST