Validation of the taxonomy data absence in the WD

Some workflow elements from the "NGS: Reads Classification" group (there are currently ten elements) require taxonomy data to be installed in the package in folder ".../data/ngs_classification/taxonomy" (see screenshots).

So, there are errors if due to some reasons the taxonomy data are not available, for example:

• "Classify Sequences with DIAMOND" returns an error like this:

  Exception with code C++ exception - Unhandled exception
  Stack dump: /var/folders/c5/_xc1z6x54w5dqt1khch9rssh0000gn/T/ugene_crashes/68F5AD00-EBCD-4006-8852-A2BEBD1E452D.dmp
  

• The program crashes on running "Classification Report".

Investigate each element and decide if validation is required for it. If it is so and the taxonomy data folder is not available show an error message on validation (please make a list of the modified elements in the comment to this issue.):

Taxonomy classification data are not available.

Also, fix the crash.