1.20 -> 1.21

Fix potential OpenGL crash when closing window.
Fix crash when closing window and parameter being automated.
Any mod files placed in the root ‘/Mods’ directory will no longer show up in the mods menu, they must be placed in a subfolder.
Fix text entry parameter changes not getting added to undo stack.
Improved undo of mouse wheel action.
Fix rare issue where knobs don’t get drawn with some graphics cards.