util.jsonschema: Fix handling of `false` as schema Schemas can be either a boolean or a table (object) but since it only checked for truthiness, the case of `false` would be handled incorrectly. There seems to be no tests that cover `then` and `else` being `false`, only a couple that check the `if` keyword.

-- Unknown platform stub
module:set_global();

-- TODO Do things that make sense if we don't know about the platform