fix: throw error for empty dataset only if fields not specified

Author: knownasilya

lib/JSON2CSVParser.js

@@ -40,7 +40,7 @@ class JSON2CSVParser extends JSON2CSVBase {
   preprocessData(data) {
     const processedData = Array.isArray(data) ? data : [data];
 
-    if (processedData.length === 0 || typeof processedData[0] !== 'object') {
+    if (!this.opts.fields && processedData.length === 0 || typeof processedData[0] !== 'object') {
       throw new Error('Data should not be empty or the "fields" option should be included');
     }
 
@@ -63,4 +63,4 @@ class JSON2CSVParser extends JSON2CSVBase {
   }
 }
 
-module.exports = JSON2CSVParser;
+module.exports = JSON2CSVParser;