FIX: Return 404 if id is not valid.

app/controllers/post_actions_controller.rb

@@ -6,6 +6,8 @@ class PostActionsController < ApplicationController
   before_filter :fetch_post_action_type_id_from_params
 
   def create
+    raise Discourse::NotFound if @post.blank?
+
     taken = PostAction.counts_for([@post], current_user)[@post.id]
 
     guardian.ensure_post_can_act!(

spec/controllers/post_actions_controller_spec.rb

@@ -31,6 +31,11 @@ describe PostActionsController do
         expect { xhr :post, :create, post_action_type_id: PostActionType.types[:like] }.to raise_error(ActionController::ParameterMissing)
       end
 
+      it 'fails when the id is invalid' do
+        xhr :post, :create, post_action_type_id: PostActionType.types[:like], id: -1
+        expect(response.status).to eq(404)
+      end
+
       it 'raises an error when the post_action_type_id index is missing' do
         expect { xhr :post, :create, id: @post.id }.to raise_error(ActionController::ParameterMissing)
       end