Color picker point sticks to bottom left and bottom right corners while mouse dragging at bottom line
Hi, can this be fixed? 
Please pay attention when the cursor moves to the bottom.

![ezgif-3-68480d9767ae](https://user-images.githubusercontent.com/4029251/100080231-a37ee680-2e56-11eb-8040-bbce2e4d0b1e.gif)

 