Default plain-text ingestion fails on empty lines

[nblumhardt]

E.g. in PowerShell, in a non-empty folder, running:

ls | seqcli ingest

Produces:

Ingestion failed: A line arrived late or could not be parsed: ``.
System.IO.InvalidDataException: A line arrived late or could not be parsed: ``.
   at SeqCli.PlainText.PlainTextLogEventReader.TryReadAsync() in C:\projects\seqcli\src\SeqCli\PlainText\PlainTextLogEventReader.cs:line 36
   at SeqCli.Ingestion.LogShipper.ReadBatchAsync(ILogEventReader reader, Func`2 filter, Int32 count, InvalidDataHandling invalidDataHandling) in C:\projects\seqcli\src\SeqCli\Ingestion\LogShipper.cs:line 94
   at SeqCli.Ingestion.LogShipper.ShipEvents(SeqConnection connection, ILogEventReader reader, List`1 enrichers, InvalidDataHandling invalidDataHandling, SendFailureHandling sendFailureHandling, Func`2 filter) in C:\projects\seqcli\src\SeqCli\Ingestion\LogShipper.cs:line 50
   at SeqCli.Cli.Commands.IngestCommand.Run() in C:\projects\seqcli\src\SeqCli\Cli\Commands\IngestCommand.cs:line 90

[nblumhardt]

This is easy to work around with --invalid-data=ignore; we should take a closer look at scenarios to see whether empty lines can be considered "valid" by the default template.

[nblumhardt]

Unsure whether we should assign bug status to this, or if the way we handle empty lines should be re-thought.