[MIRROR] fixes 2 runtimes caused by holding people up with a gun (#3283)

* fixes 2 runtimes caused by holding people up with a gun (#56800)

Fixes two runtimes, one caused by status effects always expecting a return from throw_alert, and another caused by holding yourself up (which you shouldn't even be able to do). Also fixes an issue caused by multiple people holding up the same person, when one of the perpetrators stopped holding up the victim, all of the victim's related alerts disappeared.

* fixes 2 runtimes caused by holding people up with a gun

Co-authored-by: TJatPBnJ <69724863+TJatPBnJ@users.noreply.github.com>

code/_onclick/hud/alert.dm

@@ -21,7 +21,7 @@
 	if(alerts[category])
 		thealert = alerts[category]
 		if(thealert.override_alerts)
-			return 0
+			return thealert
 		if(new_master && new_master != thealert.master)
 			WARNING("[src] threw alert [category] with new_master [new_master] while already having that alert with master [thealert.master]")
 
@@ -35,7 +35,7 @@
 				clear_alert(category)
 				return .()
 			else //no need to update
-				return 0
+				return thealert
 	else
 		thealert = new type()
 		thealert.override_alerts = override