Fix QML warnings

plugins/Toolbox/resources/qml/ToolboxAuthorPage.qml

@@ -9,7 +9,7 @@ import UM 1.1 as UM
 Item
 {
     id: page
-    property var details: base.selection
+    property var details: base.selection || {}
     anchors.fill: parent
     ToolboxBackColumn
     {
@@ -54,7 +54,7 @@ Item
                 rightMargin: UM.Theme.getSize("wide_margin").width
                 bottomMargin: UM.Theme.getSize("default_margin").height
             }
-            text: details.name
+            text: details.name || ""
             font: UM.Theme.getFont("large")
             wrapMode: Text.WordWrap
             width: parent.width
@@ -63,7 +63,7 @@ Item
         Label
         {
             id: description
-            text: details.description
+            text: details.description || ""
             anchors
             {
                 top: title.bottom

plugins/Toolbox/resources/qml/ToolboxDetailPage.qml

@@ -9,7 +9,7 @@ import UM 1.1 as UM
 Item
 {
     id: page
-    property var details: base.selection
+    property var details: base.selection || {}
     anchors.fill: parent
     width: parent.width
     ToolboxBackColumn
@@ -55,7 +55,7 @@ Item
                 rightMargin: UM.Theme.getSize("wide_margin").width
                 bottomMargin: UM.Theme.getSize("default_margin").height
             }
-            text: details.name
+            text: details.name || ""
             font: UM.Theme.getFont("large")
             color: UM.Theme.getColor("text")
             wrapMode: Text.WordWrap
@@ -106,7 +106,7 @@ Item
             spacing: Math.floor(UM.Theme.getSize("narrow_margin").height)
             Label
             {
-                text: details.version
+                text: details.version || ""
                 font: UM.Theme.getFont("very_small")
                 color: UM.Theme.getColor("text")
             }

plugins/Toolbox/resources/qml/ToolboxLicenseDialog.qml

@@ -42,7 +42,7 @@ UM.Dialog
             anchors.right: parent.right
             anchors.topMargin: UM.Theme.getSize("default_margin").height
             readOnly: true
-            text: licenseDialog.licenseContent
+            text: licenseDialog.licenseContent || ""
         }
     }
     rightButtons: