Did you change what I told you to change? With my plugin or without my plugin, using $gameActors.actor(0) will always give you an error. There is no actor with ID 0.
The error will stop if you put the right actor ID there.
That is strange.. the only way the error could continue to happening is if $gameActors.actor(1) was undefined or null. Meaning that no actor with ID 1 exist.
But you said it work fine with $gameActors.actor(1).name()
So, can you upload to me a sample project replicating the issue, so I can investigate? You can either upload it somewhere and send me the link here or send me the link through discord: hakuenstudio