fix for a bug regarding --cookie and --crawl

lib/request/basic.py

@@ -44,13 +44,15 @@ def forgeHeaders(items=None):
     the HTTP requests
     """
 
+    items = items or {}
+
+    for _ in items.keys():
+        if items[_] is None:
+            del items[_]
+
     headers = dict(conf.httpHeaders)
     headers.update(items or {})
 
-    for _ in headers.keys():
-        if headers[_] is None:
-            del headers[_]
-
     if conf.cj:
         if HTTPHEADER.COOKIE in headers:
             for cookie in conf.cj: