ignore null child collection, why not

git-svn-id: https://svn.apache.org/repos/asf/ant/core/trunk@453765 13f79535-47bb-0310-9956-ffa450edef68

src/main/org/apache/tools/ant/types/resources/Restrict.java

@@ -63,6 +63,9 @@ outer:      for (Iterator ri = w.getResourceCollection().iterator(); ri.hasNext(
         if (isReference()) {
             throw noChildrenAllowed();
         }
+        if (c == null) {
+            return;
+        }
         w.add(c);
     }