references to Entity data during a call to Icon.OnPhysicsUpdate() can crash if the entity has been destroyed.

[se5a]

There's a race condition here where the core engine can destroy and entity before the UI checks to see if the entity has been destroyed and tries to update it during the OnPhysicsUpdate calls.
SystemMapRendering is supposed to check if any of the icons related to specific entities are due for destruction before doing the physicsUpdateCalls and draws, but it appears that this is not raceproof.