Why do I get Undefined error when uploading in Dolphin?
You will get an "Undefined" error if you have set the the "Maximum uploading files number per user" or "File size" too low. Set it to a number which allows your users to upload files and this issue will get resolved. This issue may happen with video & audio settings.
For "File size", we reccomend a setting of "200" (which means, you can upload each audio/video file upto 200MB size).
The following setting can be found at:
Dolphin Admin >> Plugins >> Ray Suite >> My Widgets >> Widget Settings
Also, make sure that your folder ray/modules/music/langs have all the correct files for your current Dolphin version.