Removed NPE catches + added null checks on connection

Author: devgianlu

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

@@ -388,7 +388,7 @@ private void authenticate(@NotNull Authentication.LoginCredentials credentials)
      *                   {@code true} for {@link Session#reconnect()}.
      */
     private void authenticatePartial(@NotNull Authentication.LoginCredentials credentials, boolean removeLock) throws IOException, GeneralSecurityException, SpotifyAuthenticationException {
-        if (cipherPair == null) throw new IllegalStateException("Connection not established!");
+        if (conn == null || cipherPair == null) throw new IllegalStateException("Connection not established!");
 
         Authentication.ClientResponseEncrypted clientResponseEncrypted = Authentication.ClientResponseEncrypted.newBuilder()
                 .setLoginCredentials(credentials)
@@ -409,7 +409,6 @@ private void authenticatePartial(@NotNull Authentication.LoginCredentials creden
 
             receiver = new Receiver();
 
-
             byte[] bytes0x0f = new byte[20];
             random().nextBytes(bytes0x0f);
             sendUnchecked(Packet.Type.Unknown_0x0f, bytes0x0f);
@@ -515,11 +514,10 @@ public void close() throws IOException {
     }
 
     private void sendUnchecked(Packet.Type cmd, byte[] payload) throws IOException {
-        try {
-            cipherPair.sendEncoded(conn.out, cmd.val, payload);
-        } catch (NullPointerException e) {
-            throw new IOException(e);
-        }
+        if (conn == null)
+            throw new IOException("Cannot write to missing connection.");
+
+        cipherPair.sendEncoded(conn.out, cmd.val, payload);
     }
 
     private void waitAuthLock() {
@@ -724,7 +722,7 @@ private void reconnect() {
             synchronized (reconnectionListeners) {
                 reconnectionListeners.forEach(ReconnectionListener::onConnectionEstablished);
             }
-        } catch (NullPointerException | IOException | GeneralSecurityException | SpotifyAuthenticationException ex) {
+        } catch (IOException | GeneralSecurityException | SpotifyAuthenticationException ex) {
             if (closing)
                 return;
 
@@ -1321,8 +1319,8 @@ public void run() {
                         LOGGER.info("Skipping unknown command {cmd: 0x{}, payload: {}}", Integer.toHexString(packet.cmd), Utils.bytesToHex(packet.payload));
                         continue;
                     }
-                } catch (IOException | GeneralSecurityException | NullPointerException ex) {
-                    if (running) {
+                } catch (IOException | GeneralSecurityException ex) {
+                    if (running && !closing) {
                         LOGGER.error("Failed reading packet!", ex);
                         reconnect();
                     }