Fix build error introduced with r4168.

TBR=mflodman@webrtc.org
BUG=1837

Review URL: https://webrtc-codereview.appspot.com/1610004

git-svn-id: http://webrtc.googlecode.com/svn/trunk/webrtc@4169 4adac7df-926f-26a2-2b94-8c16560cd09d
diff --git a/modules/pacing/paced_sender.cc b/modules/pacing/paced_sender.cc
index 16629ac..d672913 100644
--- a/modules/pacing/paced_sender.cc
+++ b/modules/pacing/paced_sender.cc
@@ -205,7 +205,7 @@
     }
     return false;
   }
-  paced_sender::PacketList* packet_list;
+  paced_sender::PacketList* packet_list = NULL;
   switch (priority) {
     case kHighPriority:
       packet_list = high_priority_packets_.get();