[WIP] Fix Identify accepting empty results

[bnkai]

The identify task accepts empty results from a scraper and thus doesnt move on to the next scraper in line.
I added an extra check of the scraped scene so that if it is empty the next scraper will be used.
Also when a scraper errors out just try the next one instead of returning out

Steps to reproduce the original issue/bug

• Select a few scenes to identify ( we need scenes that the first source won't have) and add some sources
  
• Hit identify
• Even though the first scraper doesnt return any results for some of the scenes it wont continue to the next source

[bnkai]

I removed the 2 scrape error tests from the identify_test because of the when a scraper errors out just try the next one instead of returning out change. Imho if a scraper source errors out we should just skip to the next not error out. If thats not ok let me know to revert the specific change and the tests.

[WithoutPants]

I think that this checking of a valid scrape should be an expected behaviour of the source.Scraper.ScrapeScene method. That is, ScrapeScene should not be returning empty scenes.

Also, I don't think that the error tests should be removed, but should be rewritten to accomodate the new behaviour.

[bnkai]

I think that this checking of a valid scrape should be an expected behaviour of the source.Scraper.ScrapeScene method. That is, ScrapeScene should not be returning empty scenes.

Also, I don't think that the error tests should be removed, but should be rewritten to accomodate the new behaviour.

Moved the validation so that ScrapeScene returns nil if the scrape result is empty (i assume thats what should not be returning empty scenes meant ?)

Tests were adjusted and re-added with the following logic
When a scraper (source) errors out in an identify task the scrape error is ignored so we can skip to the next source. That is an error in scrape doesnt mean an error in identify

Update: There is an issue with the tagger when no results are returned from the scraper as ScrapeSingleScene should not return null results according to the schema, will investigate further

[bnkai]

Closing. Superceded by #2375