add it and make some fix ups

src/shared/GCSignal.luau

@@ -37,10 +37,12 @@ function Signal:Fire<T...>(...: T...)
 	for n: number = 1, #self.__callbacks__ do
 		self.__callbacks__[n](...)
 	end
-	self.__fired__ = false
 end
 
 function Signal:Wait()
+	if self.__fired__ then
+		self.__fired__ = false
+	end
 	repeat
 		task.wait()
 	until self.__fired__