nested options and using it

lib/cartodb/middleware/error-middleware.js

@@ -187,7 +187,7 @@ function setErrorHeader(errors, statusCode, res) {
         };
     });
     
-    res.set('X-Tiler-Errors', JSON.stringify(errorsLog));
+    res.set('X-Tiler-Errors', stringifyForLogs(errorsLog));
 }
 
 /**
@@ -198,13 +198,16 @@ function setErrorHeader(errors, statusCode, res) {
  */
 function stringifyForLogs(object) {
     Object.keys(object).map(key => {
-        const value = object[key];
-        if (object instanceof Object) {
-            stringifyForLogs(value);
-        } else {
+        if (typeof object[key] === 'object') {
+            stringifyForLogs(object[key]);
+        } else if (object[key] instanceof Array) {
+            for (let element of object[key]) {
+                stringifyForLogs(element);
+            }
+        } else if(typeof object[key] === 'string') {
             object[key] = object[key].replace(/[^a-zA-Z0-9]/g, ' ');
         }
     });
 
     return JSON.stringify(object);
-}   
+}