add null pointer check to stopword fix

source/net/yacy/search/query/SearchEvent.java

@@ -387,6 +387,7 @@ public final class SearchEvent {
         // only with the query minus the stopwords which had not been used for the search       
         boolean filtered = false;
         // check if query contains stopword
+        if (Switchboard.stopwordHashes != null) {
             Iterator<byte[]> it = query.getQueryGoal().getIncludeHashes().iterator();
             while (it.hasNext()) {
                 if (Switchboard.stopwordHashes.contains((it.next()))) {
@@ -394,6 +395,7 @@ public final class SearchEvent {
                     break;
                 }
             }
+        }
         this.snippetFetchWordHashes = query.getQueryGoal().getIncludeHashes().clone();        
         if (filtered) { // remove stopwords
             this.snippetFetchWordHashes.excludeDestructive(Switchboard.stopwordHashes);