nit fix (#19116)

modules/markup/html.go

@@ -348,8 +348,7 @@ func postProcess(ctx *RenderContext, procs []processor, input io.Reader, output
 
 	// Render everything to buf.
 	for _, node := range newNodes {
-		err = html.Render(output, node)
-		if err != nil {
+		if err := html.Render(output, node); err != nil {
 			return &postProcessError{"error rendering processed HTML", err}
 		}
 	}