The exception is most likely from https://github.com/xwiki/xwiki-commons/blob/87b757355f455d018698ead5ebbb20b2ebfdfd6f/xwiki-commons-core/xwiki-commons-extension/xwiki-commons-extension-api/src/main/java/org/xwiki/extension/internal/DefaultExtensionManager.java#L198 but it is completely unclear to me why it happens. The condition would be that in the Solr index, the extension is stored without repository ID. I also haven't been able to reproduce with Jetty.
