2D selection resize-to-cell is buggy with 1x1 selection

[HactarCE]

Steps to reproduce:

1. Create a 1x1 selection in 2D
2. Hold ctrl+shift to show selection resize preview
3. Move the mouse to the north and/or east of the selection

Expected behavior: resize preview is shown as expected, same as with 2x2 selection.

Actual behavior: resize preview does not extend beyond the northeast corner of the selection.

This behavior appears along each axis indepedently; e.g. a 1x2 selection is glitchy along one axis, but not the other.