SIP: fix a recursion bug when local IP becomes invalid (network disconnected).

Change-Id: I9adc67d2e3122f9eda5c139740c9b243cd97b08c
diff --git a/src/com/android/sip/SipServiceImpl.java b/src/com/android/sip/SipServiceImpl.java
index baf7e4c..f926905 100644
--- a/src/com/android/sip/SipServiceImpl.java
+++ b/src/com/android/sip/SipServiceImpl.java
@@ -411,7 +411,7 @@
                 // network disconnected
                 FLog.w(TAG, "resetGroup(): network disconnected?");
                 if (localIp != null) {
-                    resetGroup(localIp);
+                    resetGroup(null); // reset w/o local IP
                 } else {
                     // recursive
                     Log.wtf(TAG, "impossible!");