What's the difference between close a form by "×" button of browser and by EXIT_FROM?

hi,

My customer is using the following like to open a form window.

https://hostname:port/forms/frmservlet?config=ashisuto (opened by IE)

Reproduction:

1.open a form by the above link.

2.After open the form window ,  close the browser by "×" button of browser.

3.renew open a form by click the above link.

2,3 is  repeated about 15 times,in Java Console the following error message is output.

FRM-92091: unexpected fatal error on client-side java code" error in my application

Java Exception:

java.lang.ArrayIndexOutOfBoundsException: Array index out of range: 0

at java.util.Vector.get(Unknown Source)

at oracle.forms.handler.UICommon.updateFocus(Unknown Source)