Backward selection isn't working when selection crosses lines

[danijelz]

Describe the bug
When trying to select text bachward from some point, the selection becomes invalid when crossing the line. This happens either by using keyboard or mouse.

To Reproduce

1. Write something like

select *
from   dataset
where  age > 30

2. Set cursor position to end of text.
3. Press shift and up key or start selecting with mouse upward.

Screen recording
https://user-images.githubusercontent.com/13315108/115686442-7b3dda00-a359-11eb-9641-336254de64f6.mp4

[F0rce]

Answers in #7