[kcm] Fix showing no adapters message

We cannot rely on the number of adaptors since that changes with the
bluetooth state, but we can infer that no adapters are there based on
the rfkill state

src/kcm/package/contents/ui/Bluetooth.qml

@@ -41,7 +41,9 @@ ScrollViewKCM {
 
         Kirigami.PlaceholderMessage {
             id: noBluetoothMessage
-            visible: !BluezQt.Manager.rfkill.state === BluezQt.Rfkill.Unknown && BluezQt.Manager.adapters.length === 0
+            // We cannot use the adapter count here because that can be zero when
+            // bluetooth is disabled even when there are physical devices
+            visible: BluezQt.Manager.rfkill.state === BluezQt.Rfkill.Unknown
             text: i18n("No Bluetooth adapters found")
             width: parent.width - (Kirigami.Units.largeSpacing * 4)
             anchors.centerIn: parent