ChannelStats: Fix crash caused by expectation of __str__ being called before setValue

This assumption no longer true since
8ec873015aac3ba4193a2d498eb294975615b296.

plugins/ChannelStats/config.py

@@ -45,6 +45,10 @@ def configure(advanced):
     conf.registerPlugin('ChannelStats', True)
 
 class Smileys(registry.Value):
+    def __init__(self, *args, **kwargs):
+        self.s = ''
+        super().__init__(*args, **kwargs)
+
     def set(self, s):
         L = s.split()
         self.setValue(L)