yes, as I assumed - you delete the video (release its memory) before it can be played, so of course it is no longer defined when you try to play it after that.
Additionally, you need to place the name as a string (within '' exactly like the example for the use of this script does) for it to work correctly.
Please read and follow all instructions given in a plugin next time, in scripting every detail counts.
Please follow the example given on how to use this script.
In your first try it failed because you added a command (the release command) to it, and when I said that was wrong you not only removed the wrong release command but also the required loop structure.
And now you randomly added the isready check in the wrong way as well...
Script commands have to be used exactly as they're meant to be used - you can not randomly add them without thinking...