Added optional for Todo state

cf. https://gitlab.com/gitlab-org/gitlab/merge_requests/16837#note_217807588

app/finders/todos_finder.rb

@@ -51,7 +51,7 @@ class TodosFinder
   #
   # target - The value of the `target_type` column, such as `Issue`.
   # state - The value of the `state` column, such as `pending` or `done`.
-  def any_for_target?(target, *state)
+  def any_for_target?(target, state = nil)
     current_user.todos.any_for_target?(target, state)
   end
 

app/models/todo.rb

@@ -93,8 +93,8 @@ class Todo < ApplicationRecord
     #
     # target - The value of the `target_type` column, such as `Issue`.
     # state - The value of the `state` column, such as `pending` or `done`.
-    def any_for_target?(target, *state)
-      state.empty? ? exists?(target: target) : exists?(target: target, state: state)
+    def any_for_target?(target, state = nil)
+      state.nil? ? exists?(target: target) : exists?(target: target, state: state)
     end
 
     # Updates the state of a relation of todos to the new state.