QTextEdit don't move cursor to start in selection mode when there isn't any prev. line

I have QTextEdit with text like this:

012

345

678

When I move cursor between 4 and 5 and when I do Shift + Up there is selection of text from 2 to 4

Then when I press Shift + Up there should be selection 0-4 but it isn't.

All is working fine when I do same but in opposite direction Shift + Down

I attached patch that fix that behaviour and I don't. 

there is piece of code for SelectionNextLine so I don't understand why we are missing code for SelectPreviousLine