Fix UnsupportedOperationException during startup:
java.lang.UnsupportedOperationException: Need a SubscriptionManager
	at plugins.WebOfTrust.SubscriptionManager$Subscription.deleteWithoutCommit(SubscriptionManager.java:370)
	at plugins.WebOfTrust.SubscriptionManager.deleteAllClients(SubscriptionManager.java:1164)
	at plugins.WebOfTrust.SubscriptionManager.start(SubscriptionManager.java:1346)