Fix antimagic effect never expiring (#77500)

## About The Pull Request

Fixes #77499 

I messed this up resolving merge conflicts. 

## Changelog

🆑 Melbert
fix: Fix antimagic effect not expiring 
/🆑

code/controllers/subsystem/timer.dm

@@ -579,8 +579,8 @@ SUBSYSTEM_DEF(timer)
  * * timer_subsystem the subsystem to insert this timer into
  */
 /proc/_addtimer(datum/callback/callback, wait = 0, flags = 0, datum/controller/subsystem/timer/timer_subsystem, file, line)
-	if (!callback)
-		CRASH("addtimer called without a callback")
+	ASSERT(istype(callback), "addtimer called [callback ? "with an invalid callback ([callback])" : "without a callback"]")
+	ASSERT(isnum(wait), "addtimer called with a non-numeric wait ([wait])")
 
 	if (wait < 0)
 		stack_trace("addtimer called with a negative wait. Converting to [world.tick_lag]")