WithQueryObject encode empty values to empty string ''

[sanikoyes]

The form.EncodeToValues interface used in the WithQueryObject function will escape the empty value in the query object into an empty string "", such as the number 0, or a length 0 of array/slice/map etc.

Please provide an option to turn off this feature when create httpexpect.Expect, (the form library can create an Encoder and then call KeepZeros(false) to disable this feature)