Number of strings changes when changing ordering

**Describe the bug**

Incorrect number of empty strings after using the "Number of words" sort.

**To Reproduce the bug**

Description should look similar to this:

Steps to reproduce the behavior:

1. Go to 'Hosted Weblate -> Documentation->Polish
2. Click "Not translated strings" (4,406 strings)
3. Sort by "Number of words" (the total number of strings increases from 4,406 to 4,564)

**Screenshots**