B4J Question Open/Close port to the library jSerial

Sub Process_Globals
    Private fx As JFX
    Private MainForm As Form
    Private cmbPort As ComboBox
    Private sp As Serial
    Private astream As AsyncStreams
    Private btnClose As Button
    Private lblStatus As Label
    Private btnRefresh As Button
End Sub

Sub AppStart (Form1 As Form, Args() As String)
    MainForm = Form1
    MainForm.RootPane.LoadLayout("123") 'Load the layout file.
    MainForm.Show
    MainForm.Title = "Test"
    MainForm.BackColor = fx.Colors.White
    sp.Initialize("")
    cmbPort.Items.AddAll(sp.ListPorts)
End Sub

Sub cmbPort_SelectedIndexChanged(Index As Int, Value As Object)
    'btnOpen.Enabled = Index > -1 'enable the button if there is a selected item
    sp.Open(cmbPort.Value)
    astream.Initialize(sp.GetInputStream, sp.GetOutputStream, "astream")
    'astream.InitializePrefix(sp.GetInputStream, True, sp.GetOutputStream, "astream")
    btnRefresh.Enabled = False
    cmbPort.Enabled = False
    lblStatus.Text = "Status: Open"
End Sub

Sub btnClose_Action
    astream.Close
    sp.Close
    btnRefresh.Enabled = True
    cmbPort.Enabled = True
    lblStatus.Text = "Status: Close"
End Sub

Sub btnRefresh_Action
    sp.Initialize("")
    cmbPort.Items.Clear
    cmbPort.Items.AddAll(sp.ListPorts)
End Sub

jssc.SerialPortException: Port name - null; Method name - openPort(); Exception type - Port not found.
    at jssc.SerialPort.openPort(SerialPort.java:167)
    at anywheresoftware.b4j.serial.Serial.Open(Serial.java:80)
    at b4j.example.main._cmbport_selectedindexchanged(main.java:129)
    at sun.reflect.NativeMethodAccessorImpl.invoke0(Native Method)
    at sun.reflect.NativeMethodAccessorImpl.invoke(NativeMethodAccessorImpl.java:62)
    at sun.reflect.DelegatingMethodAccessorImpl.invoke(DelegatingMethodAccessorImpl.java:43)
    at java.lang.reflect.Method.invoke(Method.java:498)
    at anywheresoftware.b4a.BA.raiseEvent2(BA.java:79)
    at anywheresoftware.b4a.BA$1.run(BA.java:188)
    at com.sun.javafx.application.PlatformImpl.lambda$null$173(PlatformImpl.java:295)
    at java.security.AccessController.doPrivileged(Native Method)
    at com.sun.javafx.application.PlatformImpl.lambda$runLater$174(PlatformImpl.java:294)
    at com.sun.glass.ui.InvokeLaterDispatcher$Future.run(InvokeLaterDispatcher.java:95)
    at com.sun.glass.ui.win.WinApplication._runLoop(Native Method)
    at com.sun.glass.ui.win.WinApplication.lambda$null$148(WinApplication.java:191)
    at java.lang.Thread.run(Thread.java:745)