why a "modal" web popup windows stops my script?

HI

I am using IE.au3 to automate a web application.

at one point of the script, a strange behaviour occurs as follow:

I use the following code to wait that an object exists:

Do ; waiting that an object is generated (by javascript or ajax)
    Local $oPseudoButton = _IEGetObjById($oFrame,"button6_ManageDtls")
    ConsoleWrite(".") ; to see that script is going on
    Sleep(250) ; give some time to build
Until IsObj($oPseudoButton)
 
ConsoleWrite(@CRLF&"Button exist"&@CRLF) ; OK button now exist
 
_IEAction ($oButton, "click") ; here a new modal window is opened
                
                ; and script stop untill the modal windows will be closed
 
ConsoleWrite("The end")  ; only after the modal windows is closed this line is executed

but after that the click is performed by the _IEAction ($oButton, "click") statement
a new modal windows is opened with a web page inside;

the script stops in this point (line 18) and do not goes on until the modal windows is closed,

avoiding my script to do any further action.

is it normal that a modal windows stops the script?

how to free up the script from this strange interruption?