Fix crash when no server connected to tracker yet

src/clientP2P/ClientManagement.java

@@ -182,6 +182,9 @@ public abstract class ClientManagement extends ServeErrors implements Runnable {
 	 * @throws	VersionRemoteError
 	 */
 	protected String[] listDirectory() throws EmptyDirectory, InternalError, UnknownHostException, IOException, TransmissionError, ProtocolError, VersionError, SizeError, InternalRemoteError, ProtocolRemoteError, VersionRemoteError {
+		if (hostList.size() == 0) {
+			return new String[0];
+		}
 		ProtocolP2PPacket<?> d = createProtocolP2PPacket(new Payload(RequestResponseCode.LIST_REQUEST));
 		try {
 			d.sendRequest(getHostItemSocket(hostList.get(0)));