Allow sharing of empty files

Summary:
When an empty file is shared with the desktop a server is started that times-out after 10sec
this causes a notification to be displayed telling the user the transfer failed

Test Plan:
Send an empty file to the desktop
A notification should be displayed telling the user the transfer succeeded

Reviewers: #kde_connect, albertvaka

Reviewed By: #kde_connect, albertvaka

Subscribers: albertvaka, kdeconnect

Tags: #kde_connect

Differential Revision: https://phabricator.kde.org/D17176

src/org/kde/kdeconnect/Backends/LanBackend/LanLink.java

@@ -150,7 +150,7 @@ public class LanLink extends BaseLink {
 
             //Prepare socket for the payload
             final ServerSocket server;
-            if (np.hasPayload()) {
+            if (np.hasPayload() && np.getPayloadSize() != 0) {
                 server = LanLinkProvider.openServerSocketOnFreePort(LanLinkProvider.PAYLOAD_TRANSFER_MIN_PORT);
                 JSONObject payloadTransferInfo = new JSONObject();
                 payloadTransferInfo.put("port", server.getLocalPort());