Index: lucene/contrib/queries/src/java/org/apache/lucene/search/BooleanFilter.java
===================================================================
--- lucene/contrib/queries/src/java/org/apache/lucene/search/BooleanFilter.java	(revision 1207773)
+++ lucene/contrib/queries/src/java/org/apache/lucene/search/BooleanFilter.java	(working copy)
@@ -49,11 +49,11 @@
     
     for (final FilterClause fc : clauses) {
       if (fc.getOccur() == Occur.SHOULD) {
-        final DocIdSetIterator disi = getDISI(fc.getFilter(), reader);
-        if (disi == null) continue;
         if (res == null) {
           res = new FixedBitSet(reader.maxDoc());
         }
+        final DocIdSetIterator disi = getDISI(fc.getFilter(), reader);
+        if (disi == null) continue;
         res.or(disi);
       }
     }