Exception when handling Window Alert Dialogs

Question

I need to handle Windows alert dialog,clicking leave page button in the dialog should navigate from the page. I have used AutoIT script and referenced the exe in my Java code, but when the alert is displayed I see

"exception waitforpageload : [JavaScript Error: "a.document.getElementsByTagName(...)[0].getButton is not a function"

error and browser quits. Kindly help me in fixing this. Below is the AutoIT script and Java code referencing the Exe.

AutoIT script:

WinWaitActive("MyONE - Mozilla Firefox","","1000")
Sleep(70000)
 If WinExists("MyONE - Mozilla Firefox") Then

Send("{ENTER}")
 EndIf

Java Code:

     Thread.sleep(20000);
     Runtime.getRuntime().exec("C:/TestProject - DEV/test.exe");