Fix synchronisation issues

src/de/steamwar/bungeecore/Subserver.java

@@ -46,16 +46,20 @@ public class Subserver implements Runnable {
     private static final Logger logger = ProxyServer.getInstance().getLogger();
 
     public static Subserver getSubserver(ProxiedPlayer p){
+        synchronized (serverList) {
             for(int i = serverList.size()-1; i >= 0; i--){
                 if(serverList.get(i).onServer(p))
                     return serverList.get(i);
             }
+        }
         return null;
     }
     public static Subserver getSubserver(ServerInfo server){
+        synchronized (serverList) {
             for(Subserver s : serverList)
                 if(s.server == server)
                     return s;
+        }
         return null;
     }
     public static List<Subserver> getServerList(){
@@ -179,7 +183,9 @@ public class Subserver implements Runnable {
 
     public void run(){
         ProxyServer.getInstance().getServers().put(serverName, server);
+        synchronized (serverList) {
             serverList.add(this);
+        }
 
         try(BufferedReader reader = new BufferedReader(new InputStreamReader(process.getInputStream()))){
             String line = "";