don't show empty templates

src/main/java/eu/siacs/conversations/entities/Presences.java

@@ -59,8 +59,10 @@ public class Presences {
 		synchronized (this.presences) {
 			ArrayList<PresenceTemplate> templates = new ArrayList<>(presences.size());
 			for(Presence p : presences.values()) {
+				if (p.getMessage() != null && !p.getMessage().trim().isEmpty()) {
 					templates.add(new PresenceTemplate(p.getStatus(), p.getMessage()));
 				}
+			}
 			return templates;
 		}
 	}