Fix error handler

src/de/steamwar/bungeecore/Subserver.java

@@ -176,14 +176,14 @@ public class Subserver {
     }
 
     protected void register() {
-        synchronized (serverList) {
-            if(ProxyServer.getInstance().getServers().containsKey(serverName)) {
-                SecurityException e = new SecurityException("Server already registered: " + serverName);
-                stop();
-                failureCallback.accept(e);
-                throw e;
-            }
+        if(ProxyServer.getInstance().getServers().containsKey(serverName)) {
+            SecurityException e = new SecurityException("Server already registered: " + serverName);
+            stop();
+            failureCallback.accept(e);
+            throw e;
+        }
 
+        synchronized (serverList) {
             ProxyServer.getInstance().getServers().put(serverName, server);
             serverList.add(this);
             infoToServer.put(server, this);