Restore backwards compat for JavaScript protocol
templates that omit the `Port` argument.
Regression was introduced in f4f2e9f2, which
removed the fallback for empty `Port` in
`(*Request).ExecuteWithResults`, causing templates
without `Port` to be silently skipped.
Now, if no `Port` is specified, the engine
executes the JavaScript block using the target
URL's port.
Fixes#6708.
Signed-off-by: Dwi Siswanto <git@dw1.io>
746a05dac5