Taiko repl does not handle js alerts set up

[Debashis9012]

Expected behavior

Taiko repl should able to handle js alerts set up

Actual behavior

Throwing error inconvenient error

Steps to reproduce

1. openBrowser()
2. goto("http://the-internet.herokuapp.com/javascript_alerts");
3. confirm("I am a JS Confirm", async() => await dismiss());
   Its throwing the below error:

Thrown:
TypeError: Cannot read property 'exists' of undefined
    at repl.context.(anonymous function) (/usr/local/Homebrew/lib/node_modules/taiko/lib/repl.js:215:25)
    at repl:2:9
    at repl:3:3
    at Script.runInContext (vm.js:135:20)
    at Object.defaultEval (repl.js:324:29)
    at bound (domain.js:400:14)
    at Object.runBound (domain.js:413:12)

Versions

8e408c0909ca38fb2340fdc140aeffe6e94cb5bf

[Debashis9012]

This issue has been verified and found fixed with the commit version a622aa5