safer property access + style adjustments

.config/quickshell/modules/onScreenDisplay/OnScreenDisplayBrightness.qml

@@ -36,7 +36,7 @@ Scope {
     }
 
     Connections {
-        target: Audio.sink.audio
+        target: Audio.sink?.audio
         function onVolumeChanged() {
             if (!Audio.ready) return
             root.showOsdValues = false

.config/quickshell/modules/onScreenDisplay/OnScreenDisplayVolume.qml

@@ -28,7 +28,7 @@ Scope {
     }
 
     Connections {
-        target: Audio.sink.audio
+        target: Audio.sink?.audio
         function onVolumeChanged() {
             if (!Audio.ready) return
             root.triggerOsd()
@@ -97,7 +97,7 @@ Scope {
                     OsdValueIndicator {
                         id: osdValues
                         anchors.centerIn: parent 
-                        value: Audio.sink.audio.volume
+                        value: Audio.sink?.audio.volume
                         icon: "volume_up"
                         name: "Volume"
                     }

.config/quickshell/modules/onScreenDisplay/OsdValueIndicator.qml

@@ -38,6 +38,7 @@ Item {
                 Layout.leftMargin: valueIndicatorLeftPadding
                 Layout.topMargin: valueIndicatorVerticalPadding
                 Layout.bottomMargin: valueIndicatorVerticalPadding
+                color: Appearance.colors.colOnLayer0
                 text: root.icon
                 font.pixelSize: 30
             }