Resizing a selection deletes off-canvas pixels

[ZMYaro]

Describe the bug
Resizing a selection that is at least partially off the canvas when the resizing completes deletes the off-canvas pixels.

Steps to reproduce the behavior

1. Resize a selection so that part of the selection is off the canvas when resizing is complete (whether or not it was to begin with).
2. Drag the selection back onto the canvas.

Expected behavior
The resized selection is intact.

Actual behavior
Any pixels that were off the selection when the resizing was completed were removed.

[ZMYaro]

This is not a new bug, and no one has raised it before, so I am not going to rush a fix into v3.4 this late in the game, but it should be a priority if I decide to do a v3.4.1 before the next big release.