Don't show empty sections in result details

[swaterkamp]

What:
Parse empty strings in NVT tags as undefined.

Why:
Instead of undefined information we got an empty string before. This fixes showing empty sections on the result details.

How:
Check data in dev-tools and visually inspect whether the sections are no longer visible if there is no information. Added an automated test for the empty string case.

Checklist:

• Tests
• CHANGELOG Entry

[codecov]

Codecov Report

Merging #2791 (83265b7) into gsa-21.04 (74a1fd3) will decrease coverage by 0.00%.
The diff coverage is 100.00%.

❗ Current head 83265b7 differs from pull request most recent head 6a28c9d. Consider uploading reports for the commit 6a28c9d to get more accurate results

@@              Coverage Diff              @@
##           gsa-21.04    #2791      +/-   ##
=============================================
- Coverage      53.83%   53.82%   -0.01%     
=============================================
  Files           1075     1075              
  Lines          26226    26227       +1     
  Branches        7491     7492       +1     
=============================================
- Hits           14118    14116       -2     
- Misses         10993    10996       +3     
  Partials        1115     1115              

Impacted Files	Coverage Δ
gsa/src/gmp/models/nvt.js	98.94% <100.00%> (+0.01%)	⬆️
gsa/src/web/entities/container.js	44.48% <0.00%> (-1.23%)	⬇️

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[bjoernricks]

I am fine with this change too but could you please also fix the models to set undefined if an empty string is used in these tags. Such things should to be fixed in the parsing part (model) to avoid having to implement this meaning of empty string at several places in the view.

[bjoernricks]

Clicked on the wrong item. Should have been a Request changes.

changes have been implemented