Selected item in property matrix cannot be deselected

When selecting an item in the Property Matrix you cannot deselect. This affects changes you make that are supposed to be across all items selected by making them only affect the item selected.

1. Open a project with starter content
2. Open Minimal_Default level
3. Select both of the chairs and the chair
4. Open Selection in Property Matrix
5. Select a chair
   OBSERVE: you cannot deselect

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