[BUGFIX] Clear indexedNodeData cache on flush

The NodeIndexer should clear the ``indexedNodeData`` cache when
the ``flush`` method is called to avoid side effects in batch operations.

Classes/Flowpack/SimpleSearch/ContentRepositoryAdaptor/Indexer/NodeIndexer.php

@@ -140,7 +140,7 @@ public function removeNode(Node $node) {
 	 * @return void
 	 */
 	public function flush() {
-		// no operation, just here to fullfill the interface.
+		$this->indexedNodeData = array();
 	}
 
 	/**