[Port of a servicing fix for .NET 4.7-4.8]

Problem description:
If user invokes a ContextMenu (e.g. right-clicking on its owner), but the owner leaves the visual tree before the ContextMenu actually displays, the ContextMenu never displays again. This is interesting when the ContextMenu is shared by multiple owners - it won't display for other owners, even when the other owners remain in the visual tree normally.

Actual behavior:
Invoking the ContextMenu does nothing.

Expected behavior:
ContextMenu displays

Minimal repro: