Add dummy details for when there is no selection

CURA-5521

plugins/Toolbox/resources/qml/ToolboxDetailPage.qml

@@ -9,9 +9,21 @@ import UM 1.1 as UM
 Item
 {
     id: page
-    property var details: base.selection
+    property var details: base.selection || dummy_details
     anchors.fill: parent
     width: parent.width
+
+    property var dummy_details: new Object({
+        name: '',
+        version: '',
+        last_updated: '',
+        author_email: '',
+        author_name: '',
+        website: '',
+        icon_url: '',
+        download_count: ''
+    })
+
     ToolboxBackColumn
     {
         id: sidebar