Custom labels not usable and not used in sort dropdown

[jmaas-onoffice]

Cannot save custom label

Commit https://github.com/onOffice-Web-Org/oo-wp-plugin/commit/01de67715425d81d870db33218986193b2f2ee75 introcudes an error, that when you try to customize an estate field's label, it does not save and you can't add custom labels for other languages.

The browser console shows this error:

onoffice-custom-form-label.js?ver=6.1.1:32 

       Uncaught TypeError: Cannot read properties of null (reading 'text')
    at onoffice-custom-form-label.js?ver=6.1.1:32:66
    at onoffice-custom-form-label.js?ver=6.1.1:45:11
    at NodeList.forEach (<anonymous>)
    at onOffice.custom_labels_input_converter (onoffice-custom-form-label.js?ver=6.1.1:14:160)
    at onoffice-custom-form-label.js?ver=6.1.1:113:10

Custom label not used in sort dropdown

When I configure a list to be sorted by "User selection", the dropdown in the frontend does not use the custom label for the fields:

[jmaas-onoffice]

I have reverted the commit, so that we can do a release. Once fixed, you'll need to reapply the commit.

[jmaas-onoffice]

We noticed another issue with the custom labels. I think it's easiest to fix both together, so I put them both in this issue.

[dai-eastgate]

@jmaas-onoffice I fixed, you can watch video and give me feedback

https://user-images.githubusercontent.com/106214469/215996657-d4e9d145-bd51-428d-868f-a40b4b3b1ece.mp4

[jmaas-onoffice]

Looks good, thank you!