Resizing dhtmlx windows on top of iframes

I’ve noticed that when an iframe is on the page, it’s hard to resize a DHTMLX window over it. You have to move the mouse cursor very slowly in order for it to work.
This problem didn’t exist in DHTMLX 3.6, but I couldn’t figure out what it did to avoid the issue. I was able to modify DHTMLX 4.0 to put an invisible div over each iframe whenever a window was being resized, which seems to take care of it.

See the attached file for a demo of the bug (bug.html) and a demo of my fix (fixed.html). The fix itself is attached as well.
DHTMLX team: feel free to either use my fix, or some other way of working around the issue if you find one. (40.1 KB)