Sostituito ennesimo uso improprio di is not

diff --git a/RaiTV/ChannelLoader.py b/RaiTV/ChannelLoader.py
index b7d1c75..737b904 100644
--- a/RaiTV/ChannelLoader.py
+++ b/RaiTV/ChannelLoader.py
@@ -55,7 +55,7 @@ class ChannelList():
             url_array = []
             for vu in videounit:
                 url = vu.getElementsByTagName("url")[0]
-                if url.childNodes is not []:
+                if len(url.childNodes) is not 0:
                     url_array.append(url.childNodes[0].data)

             if len(url_array) is not 0: