Various bug fixes

- Fixed bug where an invalid port number would crash the program
- Closed the stage before cleaning up resources. This speeds up closing the app.
- Added error handling for when the client looses connection to the server.

Tags: #story[1281]

src/main/java/seng302/visualiser/controllers/ViewManager.java

@@ -272,6 +272,8 @@ public class ViewManager {
     }
 
     private void closeAll() {
+        if (stage!= null) stage.close();
+
         try {
             ServerAdvertiser.getInstance().unregister();
         } catch (IOException e1) {

src/main/java/seng302/visualiser/controllers/dialogs/DirectConnectController.java

@@ -50,6 +50,15 @@ public class DirectConnectController implements Initializable {
      */
     private void connectToServer() {
         //TODO fix port number validation
+
+        try{
+            Integer.parseInt(portNumber.getText());
+        }
+        catch (NumberFormatException e){
+            ViewManager.getInstance().showErrorSnackBar("You need to enter a valid port number");
+            return;
+        }
+
         ViewManager.getInstance().getGameClient()
                 .runAsClient(serverAddress.getText(), Integer.parseInt(portNumber.getText()));
     }