fix: link clicks empty array validation

app/routes.cr

@@ -4,7 +4,7 @@ module App
   before_all do |env|
     env.response.headers["Access-Control-Allow-Origin"] = "*"
     env.response.headers["Access-Control-Allow-Methods"] = "GET, POST, PUT, DELETE, OPTIONS"
-    env.response.headers["Access-Control-Allow-Headers"] = "Content-Type, Accept, X-Api-Key"
+    env.response.headers["Access-Control-Allow-Headers"] = "Content-Type, Accept, Origin, X-Api-Key"
   end
 
   after_all do |env|

app/serializers/link.cr

@@ -16,7 +16,7 @@ module App::Serializers
         builder.field("id", @link.id)
         builder.field("refer", @refer)
         builder.field("origin", @link.url)
-        builder.field("clicks", @link.clicks.map { |click| App::Serializers::Click.new(click) })
+        builder.field("clicks", @link.clicks.try(&.map { |click| App::Serializers::Click.new(click) }) || [] of App::Serializers::Click)
       end
     end
   end