PostgreSQL Search stops working when re-entering the same string twice

[dc-mst]

How to reproduce.

1. Set the search engine to Database - PostgreSQL
2. input a string which returns some results in the website search field
3. search results are shown
4. empty the search field through backspacing it
5. input the same string again
6. the search results show there are no pages in the wiki matching the input - BUG

Expected behavior: the same results should be shown every time you search for the same string.
Reproducible: always
Version: 2.5.219
Workaround: you need to reload the page to get the correct search results again

Short video showcasing the issue