tools: fix logic nit in tools/doc/generate.js

PR-URL: #19475
Reviewed-By: Colin Ihrig <cjihrig@gmail.com>
Reviewed-By: Luigi Pinca <luigipinca@gmail.com>

tools/doc/generate.js

@@ -65,8 +65,8 @@ function next(er, input) {
   switch (format) {
     case 'json':
       require('./json.js')(input, filename, (er, obj) => {
-        console.log(JSON.stringify(obj, null, 2));
         if (er) throw er;
+        console.log(JSON.stringify(obj, null, 2));
       });
       break;