Cannot start RTL selection with last character in line

[murrayju]

When using the mouse to create a selection in normal mode, it is not possible to select the last character on a line when selecting from right to left (backwards).

Steps to reproduce

1. Start with some text in the editor
2. Point the mouse beyond the last character on a line
3. Click and drag toward the start of the line

Expected

The last character on the line is part of the selection

Actual

The selection begins with the second-to-last character

Demo