Pipe don't ignore empty command

[jcubic]

Issue summary

When you create terminal with pipe extension, object interpreter, and type enter, it shows an error about invalid command

Expected behavior

enter should be ignored

Steps to reproduce

1. Open demo https://codepen.io/jcubic/pen/MWNRymN?editors=0010
2. type enter

Browser and OS

N/A

Additional notes

it can be fixed with an empty function as part of the interpreter:

const command = [{
   ...
}, function(cmd) {
    
}];