don't raise exceptions due normal usage

[galkinvv]

1. Don't raise while filling initial results into extracted category:
   the old code added 'undefined' object
   as initial single element in TMNQueries.extracted,
   and this randomly lead to problems,
   especially if actual results were not extracted
   (for example non-latin results only)

2. Don't produce network errors on Validate button
   (split feeds by | like in apply)

3. Don't raise errors on custom mostly non-latin-alphabet feeds:
   if feed returns only spaces - don't add it.

This should help #111

Tested on chrome 77.