wro4j-extensions/src/main/java/ro/isdc/wro/extensions/support/lint/ResourceLintReport.java
private List<T> filter(final Collection<T> collection) {
    final List<T> nullFreeList = new ArrayList<T>();
    if (collection != null) {
      for (final T item : collection) {
        if (item != null) {
          nullFreeList.add(item);
        }
      }
    }
    return nullFreeList;
  }
private List<T> filter(final Collection<T> collection) {
    final List<T> nullFreeList = new ArrayList<T>();
    if (collection != null) {
      for (final T item : collection) {
        if (item != null) {
          nullFreeList.add(item);
        }
      }
    }
    return nullFreeList;
  }
This filtering is required, in order to ensure that no nulls are passed (which happens when using gson for
deserializing json collection.

@param collection
to filter.
@return a null free collection of item by filtering found nulls.