Fix actionspeed modifiers with IDs being broken (#83758)

## About The Pull Request

#78124 added an init arg to these which 99% of actionspeed modifiers
don't pass, so it's passed as null, so it sets id = null, so any preset
ids get nulled out, meaning actionspeed modifiers intended on overriding
each other don't.

## Changelog

🆑 Melbert
fix: Fix some modifiers to do after speed (sanity, midas gun) stacking
when they shouldn't
/🆑

code/modules/actionspeed/_actionspeed_modifier.dm

@@ -40,7 +40,8 @@ can next move
 /datum/actionspeed_modifier/New(init_id)
 	. = ..()
 
-	id = init_id
+	if(init_id)
+		id = init_id
 
 	if(!id)
 		id = "[type]" //We turn the path into a string.