For them older camls

compiler/syntax/src/res_printer.ml

@@ -4377,7 +4377,7 @@ and print_jsx_unary_tag ~state tag_name props expr_loc cmt_tbl =
   let name = print_jsx_name tag_name in
   let formatted_props = print_jsx_props ~state props cmt_tbl in
   let tag_has_trailing_comment = has_trailing_comments cmt_tbl tag_name.loc in
-  let tag_has_no_props = List.is_empty props in
+  let tag_has_no_props = List.length props == 0 in
   let closing_token_loc =
     ParsetreeViewer.unary_element_closing_token expr_loc
   in