An implementation of Visual Basic that is built into Microsoft products.
I think that the error indicates that SelectContentControlsByTitle does not return a Content Control.
According to documentation, try this:
Dim CCtrls As ContentControls
Set CCtrls = ThisDocument.SelectContentControlsByTitle("qwe123")
If CCtrls.Count = 0 Then
Debug.Print "found nothing"
Else
' get the first found control '
Dim cc As ContentControl
Set cc = CCtrls(1)
' ...
End If