Replace that line with
var l_isJS = (os_browser != browser_not_a_browser);
I’m not entirely sure why 2.3.1 suddenly runs scripts in a different order, but it is concerning.
Sorry, when you said "that line" did you mean line 7 inside live_preinit_init_funcs() ? Am I supposed to be able to actually open the script containing that?
I thought I was able to open that script before, but I can't access the function by middle clicking on it and searching with CTRL+ T or F doesn't find anything, so I can't edit that line. I thought it was a problem on my end, so I just now removed GMLive entirely, re-imported the newest version, cleaned my IDE cache, and restarted my computer, to no avail.