Fixed AttributeError when the regular expression starts from illegal escape.
diff --git a/Lib/sre_parse.py b/Lib/sre_parse.py
index 2be392e..fb622ec 100644
--- a/Lib/sre_parse.py
+++ b/Lib/sre_parse.py
@@ -211,6 +211,7 @@
             string = str(string, 'latin1')
         self.decoded_string = string
         self.index = 0
+        self.next = None
         self.__next()
     def __next(self):
         index = self.index