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Theme throws: Error: Undefined in constant() core/lib/Drupal/Core/Asset/LibraryDiscoveryParser.php

I run a multisite installation with many different themes installed. Since yesterday, some sites throw this error beside the "The website encountered an unexpected error. Please try again later.": enter image description here

I deinstalled all themes that throw erros and set bartik as default theme for this sites. Then I rebuilt all caches and the sites are working again. But as soon as I set just one of the themes as default again, I get the same error again. Only the "CSS_MASTERSHOP" line changes to "CSS_THEMENAME". But there’s no chance all theses themes are faulty.

I found this topic https://www.drupal.org/project/void/issues/3060386 that describes a similar problem and provides a patch. But I do not even know where the "void.libraries.yml" is located.

Please, if anybody has any hint, I’d be very happy. Thank you very much in advance!

This article was republished from its original source.
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Theme throws: Error: Undefined in constant() core/lib/Drupal/Core/Asset/LibraryDiscoveryParser.php

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