Selectable entries are fetched without search query

[DiCanio]

Problem:

When using the query builder and accessing the search field (for inclusion or exclusion criteria), a search query is sent to the backend even without prior text input.

We should opt for minimizing unnecessary requests to downstream systems in order to avoid artificial load scenarios.

Steps to reproduce:

1. Open the UI in your browser
2. Navigate to "Neue Abfrage"
3. Click into the field "Code oder Suchbegriff eingeben"

Network traffic should be observable using your browser's dev tools.

Additional information:

• tested on https://feasibility.forschen-fuer-gesundheit.de
• affected version: 0.2.0-RC8 (as of noticing the issue this is deployed behind the URL stated above)