bug found using official demo

[jcyuan]

Originally I found the weird behavior from my app, then I had a test using the official demo:
http://plugins.krajee.com/file-input-ajax-demo/4
and the bug appears again.

To reproduce the bug:
1, select 3 images from disk, then click upload
2, click remove icon of the last item from the preview list to delete the last one
3, click browse to select 2 files then upload (then here 4 items in the preview list)
4, remove the last one again (3 items remaining)
5, click browse and now just select 1 file form disk and then upload, once the uploading process done you will see 5 ITEMS in the preview panel!

[jcyuan]

Man, besides I have a requirement.
Is there a way to always attach some data to ajax request? although I could use uploadExtraData or deleteExtraData or 'extra' config for each preview items but for my case:
I need to attach an Anti-Forgery token for every ajax reuqests to prevent my site from CSRF attacking.
uploadExtraData is useful for uploading, I can attach the token.
but I think there is no way to put the token into the 'extra' config which generated from the serverside.
because the token cannot be generated by server (client cookie is involved). so I need a way to modify the 'extra' config to add my token variable while deleting.
temporarily I inserted a new line:
extraData = $.extend({}, myCustomGlobalData, extraData);
at line 2249 of the source code and it works fine.
or actually there is already a way to do this but I just dont know?