[FIX] 500 error on connection when using PyWebDAV 0.9.4

(and maybe others)

Courtesy of Holger Brunn (Therp)

bzr revid: dle@openerp.com-20140411134203-lxt4mnquiiclv6w3

addons/document_webdav/webdav_server.py

@@ -93,6 +93,8 @@ def __init__(self, request, client_address, server):
         self.client_address = client_address
         self.server = server
         self.setup()
+        if hasattr(self, '_init_buffer'):
+            self._init_buffer()
 
     def get_userinfo(self, user, pw):
         return False