focus bug when using cursor keys

[dtaht]

After selecting a new plot type with the mouse, sometimes, (not always), the cursor keys remain bound to that area, even after selecting the tab of the plot with the mouse in the hope of then being able to fly through the datasets on screen.

To reproduce - select a tab from a bunch of flent.gz files, you can flip between them via the cursor keys.

Select a new plot type, select the tab again, cursor keys up/down remain bound to the plot type, left and right do nothing.