Why does slimer crash when opening a new page?

Question

JavaScript

When I click on a button, a new page opens in slimerjs. And for some reason slimer.wait(4000); when i call it. the error is like this

-> resource://slimerjs/slimer-sdk/net-log.js: 484 (in function TracingListener.prototype.onStopRequest)
         -> resource://slimerjs/slUtils.jsm: 293 (in function sleep)
         -> resource://slimerjs/slimer-sdk/slimer.jsm: 92 (in function slimer.wait)