Notification: add default icon

notificationd/qml/NotificationPopup.qml

@@ -85,11 +85,25 @@ Window {
             id: _icon
             width: 48
             height: width
-            source: "image://icontheme/%1".arg(model.iconName)
+            source: model.iconName ? "image://icontheme/%1".arg(model.iconName)
+                                   : ""
             sourceSize: Qt.size(width, height)
             Layout.alignment: Qt.AlignVCenter
             antialiasing: true
             smooth: true
+            visible: status === Image.Ready
+        }
+
+        Image {
+            id: _defaultIcon
+            width: 48
+            height: width
+            source: "image://icontheme/preferences-desktop-notification"
+            sourceSize: Qt.size(width, height)
+            Layout.alignment: Qt.AlignVCenter
+            antialiasing: true
+            smooth: true
+            visible: !_icon.visible
         }
 
         ColumnLayout {

notificationd/qml/NotificationWindow.qml

@@ -181,11 +181,25 @@ Item {
                             id: _icon
                             width: 48
                             height: width
-                            source: "image://icontheme/%1".arg(model.iconName)
+                            source: model.iconName ? "image://icontheme/%1".arg(model.iconName)
+                                                   : ""
                             sourceSize: Qt.size(width, height)
                             Layout.alignment: Qt.AlignVCenter
                             antialiasing: true
                             smooth: true
+                            visible: status === Image.Ready
+                        }
+
+                        Image {
+                            id: _defaultIcon
+                            width: 48
+                            height: width
+                            source: "image://icontheme/preferences-desktop-notification"
+                            sourceSize: Qt.size(width, height)
+                            Layout.alignment: Qt.AlignVCenter
+                            antialiasing: true
+                            smooth: true
+                            visible: !_icon.visible
                         }
 
                         ColumnLayout {