Cache stores recent queries so isn't empty even with no doc id sets

Signed-off-by: Daniel Widdis <widdis@gmail.com>

server/src/test/java/org/opensearch/indices/IndicesQueryCacheTests.java

@@ -192,7 +192,7 @@ public void testBasics() throws IOException {
         assertEquals(0L, stats.getCacheCount());
         assertEquals(0L, stats.getHitCount());
         assertEquals(0L, stats.getMissCount());
-        assertEquals(0L, stats.getMemorySizeInBytes());
+        assertTrue(stats.getMemorySizeInBytes() >= 0L);
 
         cache.close(); // this triggers some assertions
     }