modules/menusystem: add a function to reset menus' sound state

gamecore/modules/menusystem/parent.lua

@@ -58,9 +58,7 @@ function Menu:new(menusystem, name, x, y, w, h)
 
   self.depth        = 0
 
-  self.sound = {}
+  self:resetSound()
-  self.sound.asset = nil
-  self.sound.active = false
 
   self:register()
 end
@@ -252,6 +250,12 @@ end
 -- SOUND FUNCTION
 -- Handle SFX
 
+function Menu:resetSound()
+  self.sound = {}
+  self.sound.active = true
+  self.sound.asset  = nil
+end
+
 function Menu:setSound(soundasset)
   self.sound.active = true
   self.sound.asset = soundasset