Empty update query which isn't executed should reutrn a 0 count inste…

…ad of an empty observable

core/src/main/java/org/chodavarapu/datamill/db/impl/QueryBuilderImpl.java

@@ -589,7 +589,7 @@ public UpdateBuilder update(Outline<?> outline) {
     private static class EmptyUpdateSuffixBuilder implements InsertSuffixBuilder {
         @Override
         public Observable<Integer> count() {
-            return Observable.empty();
+            return Observable.just(0);
         }
 
         @Override