An empty host list is returned in Monitoring => Hosts view and Data collection => Hosts view in case if a tag that is created on host (not inherited from template) is used in host filter:

Steps to reproduce:

1. Create a host without any tags.
2. Add some tag to this host (it is important that the tag is created separately!).
3. Navigate to Monitoring => Hosts or to Data collection => Hosts
4. Use this tag in the filter, so that only the created host would be displayed
5. Apply the filter

Result: An empty host list is returned.
Expected: The host list should include the previously created host, since it matches the tag filter.