show desktop shouldn't have a background

applets/minimizeall/package/contents/ui/main.qml

@@ -41,6 +41,7 @@ Item {
     Layout.maximumHeight: inPanel ? units.iconSizeHints.panel : -1
 
     Plasmoid.preferredRepresentation: Plasmoid.fullRepresentation
+    Plasmoid.backgroundHints: PlasmaCore.Types.NoBackground
 
     Plasmoid.onActivated: toggleActive()
 

applets/showdesktop/package/contents/ui/main.qml

@@ -35,6 +35,7 @@ QtObject {
     Plasmoid.icon: plasmoid.configuration.icon
     Plasmoid.title: i18n("Show Desktop")
     Plasmoid.toolTipSubText: i18n("Show the Plasma desktop")
+    Plasmoid.backgroundHints: PlasmaCore.Types.NoBackground
 
     // QtObject has no default property
     property QtObject showdesktop: ShowDesktop { }