The minimum hits (minHits) configuration for a Query Suggestions index must be a positive integer, so while you can select a value as low as 1, setting a value of 0 will automatically reset minHits to the default of 5.
This means that a suggestion can only be valid if it returns one or more hits, as determined by the minHits setting. It's not possible to suggest a query that returns 0 hits, regardless of your configuration.