made presences synchronized

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

@@ -22,25 +22,33 @@ public class Presences {
 	}
 
 	public void updatePresence(String resource, int status) {
+		synchronized (this.presences) {
 			this.presences.put(resource, status);
 		}
+	}
 
 	public void removePresence(String resource) {
+		synchronized (this.presences) {
 			this.presences.remove(resource);
 		}
+	}
 
 	public void clearPresences() {
+		synchronized (this.presences) {
 			this.presences.clear();
 		}
+	}
 
 	public int getMostAvailableStatus() {
 		int status = OFFLINE;
+		synchronized (this.presences) {
 			Iterator<Entry<String, Integer>> it = presences.entrySet().iterator();
 			while (it.hasNext()) {
 				Entry<String, Integer> entry = it.next();
 				if (entry.getValue() < status)
 					status = entry.getValue();
 			}
+		}
 		return status;
 	}
 
@@ -61,16 +69,22 @@ public class Presences {
 	}
 
 	public int size() {
+		synchronized (this.presences) {
 			return presences.size();
 		}
+	}
 
 	public String[] asStringArray() {
+		synchronized (this.presences) {
 			final String[] presencesArray = new String[presences.size()];
 			presences.keySet().toArray(presencesArray);
 			return presencesArray;
 		}
+	}
 
 	public boolean has(String presence) {
+		synchronized (this.presences) {
 			return presences.containsKey(presence);
 		}
+	}
 }