Chat index: MissingResourceException

2021-07-27 09:01:13,308 WARN http-nio-8080-exec-4 org.sakaiproject.util.ResourceLoader - bundle 'chat' missing key: 'chat_message' from:
java.util.MissingResourceException: Can't find resource for bundle java.util.PropertyResourceBundle, key chat_message
at java.util.ResourceBundle.getObject(ResourceBundle.java:450)
at java.util.ResourceBundle.getString(ResourceBundle.java:407)
at org.sakaiproject.util.ResourceLoader.getString(ResourceLoader.java:511)
at org.sakaiproject.chat2.model.impl.ChatContentProducer.getMessageFromBundle(ChatContentProducer.java:126)
at org.sakaiproject.chat2.model.impl.ChatContentProducer.getTitle(ChatContentProducer.java:469)
at org.sakaiproject.search.elasticsearch.SiteElasticSearchIndexBuilder.addFields(SiteElasticSearchIndexBuilder.java:209)
at org.sakaiproject.search.elasticsearch.BaseElasticSearchIndexBuilder.buildIndexRequestContentSource(BaseElasticSearchIndexBuilder.java:775)