[COLLECTIONS-400] Added missing null check, thanks to Shin Hwei Tan.

git-svn-id: https://svn.apache.org/repos/asf/commons/proper/collections/trunk@1311344 13f79535-47bb-0310-9956-ffa450edef68

src/main/java/org/apache/commons/collections/CollectionUtils.java

@@ -782,6 +782,9 @@ public class CollectionUtils {
      * @since Commons Collections 3.2
      */
     public static <T> boolean addIgnoreNull(Collection<T> collection, T object) {
+        if (collection == null) {
+            throw new NullPointerException("The collection must not be null");
+        }
         return (object != null && collection.add(object));
     }