Magento 2.1 Multi Select Attribute doesn't save empty values

[Corefix]

Preconditions

1. Magento 2.1
2. Chrome 52.x

Steps to reproduce

1. Go to Magento admin
2. Go to Products > Catalog
3. Select a product that have a multi select attribute
4. Find the multi select attribute and set one or more of the options on the product (so it looks like the following image).
   
5. Save the product
6. Go back and edit the same product again.
7. Now deselect all options in the same multi select field
8. Save product again

Expected result

1. The product should now have no options selected

Actual result

1. Product have all options still selected.

It looks like the empty fields are not included in the post request, which they should, since removing values is just as important as setting them :-)

[sevos1984]

This is a known issue, internal ticket id MAGETWO-57226. Thanks for posting

[developer-lindner]

@Corefix Update to 2.1.1. and report back or close this ticket otherwise.

[nagno]

It still not works in 2.1.1. I will create a ticket on the partner portal as well. (hopefully it will get more priority)

[TClilMouse]

Still not works in 2.1.3

[nagno]

@seavenger this patch works for me: #6899

[roseofgold]

patch didn't work for me on 2.1.2

[nagno]

@roseofgold
are you sure you applied it correctly?
We are using it in a production system without any issues.

[roseofgold]

@nagno No I'm not sure. I just tried applying it again and now I can't use my admin :(

[nagno]

@roseofgold your issue is probably not related to this patch or you have an interfering customisation.
If you check the comments on the patch, @wigman created a 2.1.3 compatible version as well.