Fix reboot loop due to NPE.

All that's old is new again: http://ag/63748.

Change-Id: I83df48447dbcb7f6edf02bd07abf721b009afa49

core/java/android/net/ProxyInfo.java

@@ -160,6 +160,8 @@ public class ProxyInfo implements Parcelable {
             }
             mExclusionList = source.getExclusionListAsString();
             mParsedExclusionList = source.mParsedExclusionList;
+        } else {
+            mPacFileUrl = Uri.EMPTY;
         }
     }