ID 361767 - Keys on a negative frame value cannot be selected in the dopesheet.

Problem summary
Keys on a negative frame value cannot be selected in the dopesheet.

Customer reported version
modo.12.1v1

Customer reported platform
windows7

Steps to reproduce
1) Open Modo.
2) Create a unit cube by holding "Ctrl" and clicking the cube tool.
3) Select the "Animate" layout.
4) Select the cube created in step 2.
5) Press "Shift+W" to key the position channels on the cube.
6) Select Palettes>Dopesheet in the bottom left.
7) Hold "Alt" and left click the background to move the dopesheet timerange. Drag to the right to reveal negative frame values.
8) Select the keyframe on frame 0 and drag it to a negative frame.
9) Deselect the keyframe, then try to reselect it.
Result: The keyframe cannot be reselected.

Workaround
Marquee select the keyframe, then move it back to a positive value via the "frame" channel in the top left of the dopesheet.

Reproduced by support
This bug has been reproduced in:
12.1v1 - Windows 10, OSX 10.13.5
12.0v1 - Windows 10
11.2v3 - Windows 10
11.2v1 - Windows 10
11.1v1 - Windows 10
11.0v3 - Windows 10
10.2v4 - Windows 10, OSX 10.13.5

Earliest version tested
10.2v4 - Windows 10, OSX 10.13.5 - This issue appears to be in all versions of the product
Expected behaviour
Keys on a negative frame should be selectable.

Actual behaviour
Keys on a negative frame cannot be selected or dragged.