fix propagation of leaf reader

Author: jimczi

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

@@ -293,6 +293,7 @@ private Translog.Operation readDocAsOp(int docIndex) throws IOException {
 
     @Override
     protected void setNextSyntheticFieldsReader(LeafReaderContext context) throws IOException {
+        super.setNextSyntheticFieldsReader(context);
         if (syntheticVectorPatchLoader != null) {
             syntheticVectorPatchLoaderLeaf = syntheticVectorPatchLoader.leaf(context);
         }