Fix the build

Check for null before trying to make InetAddresses.

Change-Id: I3228eea32eb455437dd76be2de56a913884f3f6e
diff --git a/core/java/android/net/NetworkUtils.java b/core/java/android/net/NetworkUtils.java
index 1c48e7d..97f96da 100644
--- a/core/java/android/net/NetworkUtils.java
+++ b/core/java/android/net/NetworkUtils.java
@@ -162,8 +162,8 @@
         // TODO - do this for real, using a hidden method on InetAddress that aborts
         // instead of doing dns step
         if (!InetAddress.isNumeric(addrString)) {
-            throw new IllegalArgumentException("numericToInetAddress with non numeric: " +
-                    addrString);
+            throw new IllegalArgumentException("numericToInetAddress with non numeric: '" +
+                    addrString + "'");
         }
         try {
             return InetAddress.getByName(addrString);