fix

Author: ChrisHegarty

server/src/main/java/org/elasticsearch/index/engine/Engine.java

@@ -301,14 +301,15 @@ public DenseVectorStats denseVectorStats(MappingLookup mappingLookup) {
     protected final DenseVectorStats denseVectorStats(IndexReader indexReader, List<DenseVectorFieldMapper> fields) {
         // we don't wait for a pending refreshes here since it's a stats call instead we mark it as accessed only which will cause
         // the next scheduled refresh to go through and refresh the stats as well
+        var stats = new DenseVectorStats();
         for (LeafReaderContext readerContext : indexReader.leaves()) {
             try {
-                return getDenseVectorStats(readerContext.reader(), fields);
+                stats.add(getDenseVectorStats(readerContext.reader(), fields));
             } catch (IOException e) {
                 logger.trace(() -> "failed to get dense vector stats for [" + readerContext + "]", e);
             }
         }
-        return new DenseVectorStats();
+        return stats;
     }
 
     private DenseVectorStats getDenseVectorStats(final LeafReader atomicReader, List<DenseVectorFieldMapper> fieldMappers)