Since rP23680, it is possible for units to be sent "Attacked" messages even though they cannot be attacked
(e.g. a non-capturable being the target of a Capture attack effect).
This seems bad for a few reasons:
- performance. Messages get sent for no reason
- likely source of bug.
- general cleanliness of the code.
This fixes it and adds a test.
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As noted by @Angen [[ code.wildfiregames.com/D2738#116269 | here ]].