nasdaq/soupfile: Fix parsing of unknown messages
nasdaq/soupfile: Fix parsing of unknown messages

The message parser can return zero to indicate an unknown message. Fix
SoupFILE parsing to deal with that.

Signed-off-by: Pekka Enberg <add4fcd06328a394f0ad91feda7ee057316dc5ed@iki.fi>

penberg/helix,penberg/helix,jvirtanen/helix,jvirtanen/helix