Deleting a TMA grid deletes all regions

[SoerenXD]

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Bug report

Describe the bug
If a TMA grid has been assigned using the TMA dearrayer and the TMA grid is removed later, it will remove all regions along with it, regardless of whether they have been placed n the hierachy or not.

To Reproduce
Steps to reproduce the behavior:

1. Open a TMA image
2. Draw some regions in the TMA cores
3. Run the TMA de-arrayer
4. Delete the TMA-grid
5. All manually drawn regions are gone.

Expected behavior
The TMA grid should be removed and the other regions should be kept.

Screenshots
If applicable, add screenshots to help explain your problem.

Desktop (please complete the following information):

• OS: Windows
• QuPath Version 0.2.3

Additional context
Add any other context about the problem here.

[petebankhead]

Thanks, I can reproduce the behavior - the entire object hierarchy is removed.
Furthermore, clearTMAGrid() no longer works from a script.

[petebankhead]

This script may be useful as a workaround, but I haven't checked if it has any unwelcome side-effects. The bug will need fixed in a later release.

def hierarchy = getCurrentHierarchy()
hierarchy.clearTMAGrid()
hierarchy.tmaGrid = null
fireHierarchyUpdate()

[petebankhead]

The changes in petebankhead@deea6c7 have hopefully resolved the issue, and will be available in v0.3.
Please do reopen this if you find that it hasn't been fixed after all.