Remove Page button not working

Expected behaviour
The Confirmation Popup should close and the page should be remove

Link to document
This issue is coming in the demo as well :

Code snippet
Error coming in Console :
Uncaught TypeError: Cannot read property ‘then’ of undefined
at Object.onConfirm (webviewer-ui.min.js:formatted:57274)
at webviewer-ui.min.js:formatted:67683
at Object.l (webviewer-ui.min.js:formatted:16219)
at p (webviewer-ui.min.js:formatted:16237)
at webviewer-ui.min.js:formatted:16246
at v (webviewer-ui.min.js:formatted:16256)
at at (webviewer-ui.min.js:formatted:17007)
at ot (webviewer-ui.min.js:formatted:16996)
at lt (webviewer-ui.min.js:formatted:17018)
at pt (webviewer-ui.min.js:formatted:17096)

Line which is giving error:
onConfirm: function() {
return Ct.removePages(a).then((function() {

Issue fixed + explained here