Data needs to exist in ES for pattern definition

[markwalkom]

When you define an index pattern, there needs to be indices with this pattern in Elasticsearch and there also needs to be data in those indices. While this seems obvious, there seems to be an increasing number of people that miss this and create threads on the forums, so I think we should be explicit and remove any possible ambiguity.

Here.

We could also link to here to help users index/import data.

[palecur]

Fixed in the 4.4 release.