DATACOUCH-151 - Fixed NullPointerException on auto-boxing in CouchbaseTemplate.

Original pull request: #55.

src/main/java/org/springframework/data/couchbase/core/CouchbaseTemplate.java

@@ -316,7 +316,8 @@ public class CouchbaseTemplate implements CouchbaseOperations, ApplicationEventP
           if (cas == CASResponse.EXISTS) {
             throw new OptimisticLockingFailureException("Saving document with version value failed: " + cas);
           } else {
-            long newCas = casFuture.getCas();
+            Long casValue = casFuture.getCas();
+            long newCas = (casValue == null) ? 0 : casValue.longValue();
             accessor.setProperty(versionProperty, newCas);
             return true;
           }