return None instead of -1 in case of invalid index

diff --git a/lib/python/Components/Sources/List.py b/lib/python/Components/Sources/List.py
index d722129..8250440 100644 (file)
--- a/lib/python/Components/Sources/List.py
+++ b/lib/python/Components/Sources/List.py
@@ -49,7 +49,7 @@ to generate HTML."""
                if self.master is not None:
                        return self.master.index
                else:
-                       return -1
+                       return None
 
        setCurrentIndex = setIndex