Fix search for non-existing term with filters turned on.

Task-number: QTBUG-26733

In case we search with attributes, all fields including the actual
search term needs to match. Otherwise we will find all pages with
matching indexed filter attributes, but ignoring the search term...

Change-Id: I691afb839a4175e800ab71a40ead7963f3c54c31
Reviewed-by: Christian Kandeler <christian.kandeler@digia.com>

src/assistant/help/qhelpsearchindexreader_clucene.cpp

@@ -269,7 +269,7 @@ bool QHelpSearchIndexReaderClucene::buildTryHarderQuery(
         return false;
     if (isNegativeQuery(query))
         return false;
-    if (!addDefaultQuery(query, fieldName, false, booleanQuery, analyzer))
+    if (!addDefaultQuery(query, fieldName, !filterAttributes.isEmpty(), booleanQuery, analyzer))
         return false;
     if (filterAttributes.isEmpty())
         return true;