Sync won't start on empty PVOutput system

[CodeCasterNL]

When syncing into a new PVOutput system, it'll return a 400 Bad Request when querying summaries:

2022-07-20 12:08:12,328 [7] WARN InputToOutputWriter+d__5 - Could not retrieve input summaries from PVOutput between 07/07/2022 00:00:00 and 07/20/2022 12:08:10

https://gathering.tweakers.net/forum/list_message/72187580#72187580

Handle that as "no data" and sync anyway.