796fa7
@@ -46,6 +46,9 @@
   public static <T> Set<T> findOperators(Collection<Operator<?>> starts, Class<T> clazz) {
     Set<T> found = new HashSet<T>();
     for (Operator<?> start : starts) {
+      if (start == null) {
+        continue;
+      }
       findOperators(start, clazz, found);
     }
     return found;
