For resizable columns, if you try to grab the grip handle in the small area where the cursor doesn't activate, it throws an undefined event warning. Dragging over the blue while the cursor activates for dragging works fine. The issue is when your cursor doesn't activate but you're still hovering over the blue portion of the column. In that small section, if you click on it (which there is a strong likelihood you may) you will get a "cannot read properties of undefined "i"" exception which essentially means you have an undefined event being triggered.
For resizable columns, if you try to grab the grip handle in the small area where the cursor doesn't activate, it throws an undefined event warning. Dragging over the blue while the cursor activates for dragging works fine. The issue is when your cursor doesn't activate but you're still hovering over the blue portion of the column. In that small section, if you click on it (which there is a strong likelihood you may) you will get a "cannot read properties of undefined "i"" exception which essentially means you have an undefined event being triggered.