We just moved one of our applications from v 8.3 to V 9.
We had some custom queries / custom lists with HTML and conditional logic.
The conditional logic that broke looked similar to this:
# if(data["ExtraInfo"] != undefined) { #
<div>{ExtraInfo}</div>
# } #
# if(data["ExtraInfo"] == undefined) { #
<div>No info</div>
# } #
It works again after we made this change:
# if(data["ExtraInfo"] != "") { #
<div>{ExtraInfo}</div>
# } #
# if(data["ExtraInfo"] == "") { #
<div>No info</div>
# } #