Catch situations where backend is not correctly set

resources/qml/SaveButton.qml

@@ -14,7 +14,7 @@ Item {
 
     property real progress: UM.Backend.progress
     property int backendState: UM.Backend.state
-    property var backend: CuraApplication.getBackend()
+    property var backend: CuraApplication.getBackend() || "undefined"
     property bool activity: CuraApplication.platformActivity
 
     property alias buttonRowWidth: saveRow.width
@@ -49,12 +49,16 @@ Item {
     }
 
     function sliceOrStopSlicing() {
-        if (base.backendState != "undefined" && backend !== "undefined") {
-            if ([1, 5].indexOf(base.backendState) != -1) {
-                backend.forceSlice();
-            } else {
-                backend.stopSlicing();
+        try {
+            if (base.backendState != "undefined" && base.backend != "undefined") {
+                if ([1, 5].indexOf(base.backendState) != -1) {
+                    backend.forceSlice();
+                } else {
+                    backend.stopSlicing();
+                }
             }
+        } catch (e) {
+            console.log('Could not start or stop slicing', e)
         }
     }