Remove debug behavior

Contributes to CL-1157

plugins/UM3NetworkPrinting/resources/qml/MonitorQueue.qml

@@ -159,7 +159,7 @@ Item
                 }
                 printJob: modelData
             }
-            model: OutputDevice.receivedPrintJobs ? OutputDevice.queuedPrintJobs.concat([null,null]) : [null,null]
+            model: OutputDevice.receivedPrintJobs ? OutputDevice.queuedPrintJobs : [null,null]
             spacing: 6  // TODO: Theme!
         }
     }

plugins/UM3NetworkPrinting/resources/qml/MonitorStage.qml

@@ -67,7 +67,7 @@ Component
             MonitorCarousel
             {
                 id: carousel
-                printers: OutputDevice.printers.concat([null])
+                printers: OutputDevice.receivedPrintJobs ? OutputDevice.printers : [null]
             }
         }