qml: LoadingWalletDialog: fix ressource leak

When closing the OpenWalletDialog without unlocking a wallet the
LoadingWalletDialog wouldn't get properly cleaned up as the
LoadingWalletDialog.visible was never set true. This causes the
connections to accumulate and the callbacks won't get unregistered after
closing the LoadingWalletDialog again.

electrum/gui/qml/components/LoadingWalletDialog.qml

@@ -44,7 +44,13 @@ ElDialog {
             console.log('daemon loading ' + Daemon.loading)
             if (!Daemon.loading) {
                 showTimer.stop()
-                dialog.close()
+                if (dialog.visible) {
+                    dialog.close()
+                } else {
+                    // if the dialog wasn't visible its onClosed callbacks don't get called, so it
+                    // needs to be destroyed manually
+                    Qt.callLater(function() { dialog.destroy() })
+                }
             }
         }
     }