[FIX] auth_oauth: avoid double slashed redirect urls

addons/auth_oauth/controllers/main.py

@@ -70,9 +70,9 @@ class OAuthLogin(Home):
         return providers
 
     def get_state(self, provider):
-        redirect = request.params.get('redirect', 'web')
+        redirect = request.params.get('redirect') or 'web'
         if not redirect.startswith(('//', 'http://', 'https://')):
-            redirect = '%s%s' % (request.httprequest.url_root, redirect)
+            redirect = '%s%s' % (request.httprequest.url_root, redirect[1:] if redirect[0] == '/' else redirect)
         state = dict(
             d=request.session.db,
             p=provider['id'],