duplicate on (multi)select attribute breaks validation

[Schrank]

Preconditions (*)

Demo build on the demo store of basecom: https://www.basecom.de/magento2/demo
Magento Ver.-2.2.6

On (multi)select attributes it is possible to save duplicates. The validation is correct, but for some reason the list of options is hidden after validation and not validated again due to that.

Steps to reproduce (*)

1. Open product attribute "activity"
2. add new option "Urban"
   
   
3. Click on Save Attribute
4. Click a second time on "Save Attribute"

Expected result (*)

1. Error is shown on the two options
2. List of options does not vanish
3. after correction the attribute is saved WITHOUT duplicate

Actual result (*)

1. List of Attributes vanishes
   
2. See the error triangle on the tab on the left
3. The attribute is saved WITH duplicate

Might be connected to #7646

[magento-engcom-team]

Hi @Schrank. Thank you for your report.
To help us process this issue please make sure that you provided the following information:

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• Information on your environment
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Please make sure that the issue is reproducible on the vanilla Magento instance following Steps to reproduce. To deploy vanilla Magento instance on our environment, please, add a comment to the issue:

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@Schrank do you confirm that you was able to reproduce the issue on vanilla Magento instance following steps to reproduce?

• yes
• no

[magento-engcom-team]

Hi @dmytro-ch. Thank you for working on this issue.
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[magento-engcom-team]

@dmytro-ch Thank you for verifying the issue. Based on the provided information internal tickets MAGETWO-96743 were created

[dmytro-ch]

Hello @Schrank, thank you for the report.
I've reproduced the issue for latest Magento 2.2 version.
It also looks like the issue has been allready fixed for Magento 2.3.

[Schrank]

Good to read, thanks @dmytro-ch