Fix revoke callbacks being run for `false` values passed to `set_privileges`

stuff.diff

diff --git a/builtin/game/auth.lua b/builtin/game/auth.lua
index fa1860d5d..932021a0e 100644
--- a/builtin/game/auth.lua
+++ b/builtin/game/auth.lua
@@ -101,7 +101,7 @@ core.builtin_auth_handler = {
 
 		-- Run revoke callbacks
 		for priv, _ in pairs(prev_privs) do
-			if not privileges[priv] then
+			if privileges[priv] == nil then
 				core.run_priv_callbacks(name, priv, nil, "revoke")
 			end
 		end