Solve #182 add table pool for events

druid/base/back_handler.lua

@@ -30,6 +30,12 @@ function BackHandler.init(self, callback, params)
 end
 
 
+function BackHandler.on_internal_remove(self)
+	component.on_internal_remove(self)
+	self.on_back:clear()
+end
+
+
 --- Input handler for component
 -- @tparam BackHandler self @{BackHandler}
 -- @tparam string action_id on_input action id