Refresh the AP pool after stopping the receiver

Before, we tried to refresh the AP pool before stopping the receiver. If the AP pool refresh failed it would throw an exception and the receiver would not be stopped, making it trying to access a null pointer afterwards. This should fix #447.

Author: iscle

lib/src/main/java/xyz/gianlu/librespot/core/Session.java

@@ -718,13 +718,13 @@ private void reconnect() {
         }
 
         try {
-            apResolver.refreshPool();
-
             if (conn != null) {
-                conn.socket.close();
                 receiver.stop();
+                conn.socket.close();
             }
 
+            apResolver.refreshPool();
+
             conn = ConnectionHolder.create(apResolver.getRandomAccesspoint(), inner.conf);
             connect();
             authenticatePartial(Authentication.LoginCredentials.newBuilder()