How to allow empty param values in data explorer?

I would like to allow a filtering step to be optional, but if I leave the query field empty, I get an error:

--- string :query = '%'
select uh.details 
from user_histories uh
where uh.details like case 
      when :query is not null then '%' || :query || '%'
      else '%'
limit 5

Error: DataExplorer::ValidationError: Missing parameter query of type string

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