Player entity invalid during OnPluginEnd

[nosoop]

Splitting this issue off from #53.

L 04/20/2024 - 02:34:17: [SM] Exception reported: Entity 1 (1) is invalid
L 04/20/2024 - 02:34:17: [SM] Blaming: tf2attributes.smx
L 04/20/2024 - 02:34:17: [SM] Call stack trace:
L 04/20/2024 - 02:34:17: [SM] [0] GetEntityAddress
L 04/20/2024 - 02:34:17: [SM] [1] Line 980, C:\tf2serverff2\steamapps\common\Team Fortress 2 Dedicated Server\tf\addons\sourcemod\scripting\tf2attributes.sp::GetEntityAttributeList
L 04/20/2024 - 02:34:17: [SM] [2] Line 1195, C:\tf2serverff2\steamapps\common\Team Fortress 2 Dedicated Server\tf\addons\sourcemod\scripting\tf2attributes.sp::RemoveNonNetworkedRuntimeAttributesOnEntities
L 04/20/2024 - 02:34:17: [SM] [3] Line 375, C:\tf2serverff2\steamapps\common\Team Fortress 2 Dedicated Server\tf\addons\sourcemod\scripting\tf2attributes.sp::OnPluginEnd