assume timestamp of logentries without correct timestamp

[marcmo]

for some logfiles we see an invalid timestamp in the beginning

0000-00-00 00:00:00.249: abc

and only after some time we get a real timestamp

2019-07-12 16:16:51.394: LIFECYCLE

in those cases we will report errors for all lines until we get a valid timestamp. what we could do is to apply the first valid timestamp to all previous lines. that would not give the perfect timestamp but at least recover enough to do somewhat meaningful merging.