Caused by: java.lang.UnsupportedOperationException
	at java.base/java.util.AbstractCollection.add(AbstractCollection.java:267)
	at org.ametys.plugins.pagesubscription.PageSubscriptionDAO.addSubscriber(PageSubscriptionDAO.java:132)
	at org.ametys.plugins.pagesubscription.PageSubscribeAction.act(PageSubscribeAction.java:104)
	at org.apache.cocoon.components.treeprocessor.sitemap.ActTypeNode.invoke(ActTypeNode.java:120)
	at org.apache.cocoon.components.treeprocessor.AbstractParentProcessingNode.invokeNodes(AbstractParentProcessingNode.java:47)
	at org.apache.cocoon.components.treeprocessor.sitemap.MatchNode.invoke(MatchNode.java:108)
	at org.apache.cocoon.components.treeprocessor.AbstractParentProcessingNode.invokeNodes(AbstractParentProcessingNode.java:69)
	at org.apache.cocoon.components.treeprocessor.sitemap.PipelineNode.invoke(PipelineNode.java:143)
	at org.apache.cocoon.components.treeprocessor.AbstractParentProcessingNode.invokeNodes(AbstractParentProcessingNode.java:69)
	at org.apache.cocoon.components.treeprocessor.sitemap.PipelinesNode.invoke(PipelinesNode.java:93)
	at org.apache.cocoon.components.treeprocessor.ConcreteTreeProcessor.process(ConcreteTreeProcessor.java:236)
	at org.apache.cocoon.components.treeprocessor.ConcreteTreeProcessor.process(ConcreteTreeProcessor.java:178)
	at org.apache.cocoon.components.treeprocessor.TreeProcessor.process(TreeProcessor.java:254)
	at org.apache.cocoon.components.treeprocessor.sitemap.MountNode.invoke(MountNode.java:118)
	... 54 more