Big mistery on DA.GetDataTree with optional inputs

Hi all,

I am currently blocking on something really weird:

I cannot do any

If (not DA.GetDataTree(n, something)) then ...

test with any optional inputs.

With GetDataList it's working perfectly.

I even tried to switch between 3.5 or 4.0, but nothing is changing.

Example:

(List, working)

Protected Overrides Sub RegisterInputParams(pManager As Grasshopper.Kernel.GH_Component.GH_InputParamManager)
pManager.Register_StringParam("TestString", "TestString", "OPTIONAL // TestString.", GH_ParamAccess.list)
pManager(0).Optional = True
End Sub

Protected Overrides Sub RegisterOutputParams(pManager As Grasshopper.Kernel.GH_Component.GH_OutputParamManager)
pManager.Register_StringParam("Test", "Test", "Test")
End Sub

Protected Overrides Sub SolveInstance(DA As Grasshopper.Kernel.IGH_DataAccess)

Dim TestString As New List(Of String)
Dim Log As New List(Of String)

If (Not DA.GetDataList(0, TestString)) Then
Log.Add("Blop")
DA.SetDataList(0, Log)
End If

End Sub
End Class

(Tree, not working)

Protected Overrides Sub RegisterOutputParams(pManager As Grasshopper.Kernel.GH_Component.GH_OutputParamManager)
pManager.Register_StringParam("Test", "Test", "Test")
End Sub

Protected Overrides Sub SolveInstance(DA As Grasshopper.Kernel.IGH_DataAccess)

Dim TestString As New Grasshopper.Kernel.Data.GH_Structure(Of Grasshopper.Kernel.Types.GH_String)
Dim Log As New List(Of String)

If (Not DA.GetDataTree(0, TestString)) Then
Log.Add("Blop")
DA.SetDataList(0, Log)
End If

End Sub
End Class

I have been searching an error somewhere all the day, and I really don't get it... it's doing the same thing with any data type...

Any clues? It really drives me crazy...