Merge pull request #4564 from jacty/patch-1

Unnecessary update when value is None

scrapy/settings/__init__.py

@@ -82,7 +82,8 @@ class BaseSettings(MutableMapping):
     def __init__(self, values=None, priority='project'):
         self.frozen = False
         self.attributes = {}
-        self.update(values, priority)
+        if values:
+            self.update(values, priority)
 
     def __getitem__(self, opt_name):
         if opt_name not in self: