HSEARCH-2662 Lucene: Fix behavior when querying dynamically sharded i…

…ndexes with no shard

We used to throw an NPE at some point. We may as well not try to search
at all, since we know there won't be any result from the start.

engine/src/main/java/org/hibernate/search/query/engine/impl/LuceneHSQuery.java

@@ -458,6 +458,13 @@ private LazyQueryState buildSearcher(ExtendedSearchIntegrator extendedIntegrator
 		}
 		this.idFieldNames = idFieldNames;
 
+		if ( targetedIndexes.isEmpty() ) {
+			/*
+			 * May happen when searching on indexes with dynamic sharding that haven't any shard yet.
+			 */
+			return null;
+		}
+
 		//compute optimization needClassFilterClause
 		//if at least one DP contains one class that is not part of the targeted classesAndSubclasses we can't optimize
 		if ( classesAndSubclasses != null ) {