BScrollBar left arrow wont decrement when thumb all the way to left but value still > 1

[smallstepforman]

Set the scrollbar range to (0, 10'000). Move the scroll bar right, then all the way to the left. See #17079 and the scroll value is not 0, it's higher (say 21). Pressing the left arrow will NOT decrement the value. However, if the scroll bar is moved a fraction to the right (so that the value is 40), then pressing the left arrow will decrement the value (all the way to 1).