Decorators don't apply on Default Search page

When a decorator is created for the Default search, it doesn't seem to take affect.

## Expected Behavior
Decorators created for default search should apply on /search page

## Current Behavior
Decorator is not applied, the field is not created or modified.

## Possible Solution
N/A

## Steps to Reproduce (for bugs)

1. Create decorator for Default Search
2. Perform search on /search page

You will observe no decorator applied

## Context
I am finally getting rid of an old Graylog 2 install where we make extensive use of decorators on the search page. I need to replicate those decorators but the only way I can get decorators to apply currently is to go in and search in a stream rather than on /search.

## Your Environment

* Graylog Version: 6.1.4


It may be that this is no longer supported when it was years ago, but the definition of default search suggests it should. If not, it is a big step backwards in usability,