Code passed but does not do what expected

Hi, in error handling course for in the Handling Error task I seemed to have managed to get my code to pass the test but in Xcode playground I cannot get it to output the way I think it should. In the below code my believe is that it should print "The dictionary was empty" as the value in data is nil. But in my case it does not print anything. Any clues why?

enum ParserError: Error { case emptyDictionary case invalidKey }

struct Parser { var data: [String : String?]? //think remove ? at end

func parse() throws {
    guard let iData = data else {
        throw ParserError.emptyDictionary
    }

    guard let keysArray = data?.keys, keysArray.contains("someKey") else {
        throw ParserError.invalidKey
    }

    //wrie in here happy code
}

}

let data: [String : String?]? = ["someKey": nil] let parser = Parser(data: data)

do { try parser.parse() } catch ParserError.emptyDictionary(let emptyDic) { print("The dictionary was empty") } catch ParserError.invalidKey(let invalidKey) { print("the dictionary did not contain the specified key") }