catch utf8 error

gen_stats

@@ -25,7 +25,11 @@ def unsanitize(node, default=""):
             v = node.text + "=" * (4 - missing_padding)
         else:
             v = node.text
-        return base64.b64decode(v).decode("utf-8")
+
+        try:
+            return base64.b64decode(v).decode("utf-8")
+        except:
+            return "failed to read topic as utf-8"
 
     return node.text