Filedownload with file name contain empty string become to "+" sign in IE

<zk>
	<zscript><![CDATA[
	import org.zkoss.zul.Filedownload;
	import java.io.InputStream;
	import java.io.ByteArrayInputStream;
	import org.zkoss.util.media.AMedia;
	import java.net.URLEncoder;
	import org.zkoss.lang.Strings;
	
	void download() throws Exception {
		InputStream is = new ByteArrayInputStream("test".getBytes("utf-8"));
		AMedia media = new AMedia("測 試", "txt", "text/plain", is);
		Filedownload.save(media);
	}
	]]></zscript>
	<button label="download" onClick="download()">
	</button>
</zk>