Application Keeps Crashing When I Try To Add A Value To An Array / Fix It?

I have some java script in my vb.net application and I've been trying to figure out why my web app keeps crashing when i try to instantiate an array (i placed a comment where the app is crashing in the code below). Here's my code...

Hopefully the code above is enough for to figure out the issue. However, here's a mini recap of what's going on. A user selected a value from firstListBox and the function above copies it over to secondListBox. The code in the first condition works fine, but the code in the else block doesn't. Now, here's the catch/difference between the if and else statement...the Else block is basically doing the same thing as the if statement, except the values that needs to be copied are coming from a session variable (hdnSessionVariable = '<%=Session("playerId")%>'. I've commented out every line in the else statement and the app works until it hits the secondListBox.options[secondListBox.options.length] = newOption line. Anybody have any idea what's wrong here?