From 55ba2c2b3c6f7e057c7214899206a239dd1354dd Mon Sep 17 00:00:00 2001
From: "Zheng, Lei" <realthunder.dev@gmail.com>
Date: Wed, 21 Mar 2018 15:43:28 +0800
Subject: [PATCH] constraint: tolerate empty lock constraint

---
 constraint.py | 2 +-
 1 file changed, 1 insertion(+), 1 deletion(-)

diff --git a/constraint.py b/constraint.py
index 2c4a6ce..0064c60 100644
--- a/constraint.py
+++ b/constraint.py
@@ -463,7 +463,7 @@ class Constraint(ProxyType):
 
         if not found:
             if not firstInfo:
-                return None
+                return ret
             if utils.isDraftObject(firstInfo.Part):
                 Locked.lockElement(firstInfo,solver)
                 logger.debug('lock first draft object {}'.format(