Velo decoder crash on missing bank

Fixes a crash caused by missing RAW banks triggering an attempt to create two decoder status objects in the same TES location.

This condition occurs when trying to decode TAE data when there is none. This scenario is common in online monitoring tasks.

This also happens in some DaVinci jobs that are decoding locations in stripped DSTs that do not have the VELO banks present.

This bug was introduced in LHCb v42r1 and so affects DaVinci v42r2 and v42r3 unfortunately.

The source branch is 2017-pacthes + commit 05894812, the branch Velo_decoder_tae_crash should also be removed after this merge is successful.