Check file exists before trying to take backup

packages/node_modules/@node-red/runtime/lib/storage/localfilesystem/util.js

@@ -80,7 +80,7 @@ module.exports = {
     */
     writeFile: function(path,content,backupPath) {
         var backupPromise;
-        if (backupPath) {
+        if (backupPath && fs.existsSync(path)) {
             backupPromise = fs.copy(path,backupPath);
         } else {
             backupPromise = Promise.resolve();