Canceling sending job to cluster no longer results in "still sending print" message.

Previously it would always show this, requiring a restart of Cura before print could be sent. CL-913

plugins/UM3NetworkPrinting/PrintWindow.qml

@@ -90,6 +90,7 @@ UM.Dialog
             onClicked: {
                 base.visible = false;
                 printerSelectionCombobox.currentIndex = 0
+                OutputDevice.cancelPrintSelection()
             }
         }
     ]