track screens count changes for View Settings

app/settings/universalsettings.cpp

@@ -63,6 +63,9 @@ UniversalSettings::UniversalSettings(KSharedConfig::Ptr config, QObject *parent)
     connect(this, &UniversalSettings::versionChanged, this, &UniversalSettings::saveConfig);
 
     connect(this, &UniversalSettings::screenScalesChanged, this, &UniversalSettings::saveScalesConfig);
+
+    connect(qGuiApp, &QGuiApplication::screenAdded, this, &UniversalSettings::screensCountChanged);
+    connect(qGuiApp, &QGuiApplication::screenRemoved, this, &UniversalSettings::screensCountChanged);
 }
 
 UniversalSettings::~UniversalSettings()

app/settings/universalsettings.h

@@ -140,6 +140,7 @@ signals:
     void layoutsMemoryUsageChanged();
     void metaPressAndHoldEnabledChanged();
     void mouseSensitivityChanged();
+    void screensCountChanged();
     void screenScalesChanged();
     void screenTrackerIntervalChanged();
     void showInfoWindowChanged();

declarativeimports/components/ComboBox.qml

@@ -156,7 +156,17 @@ T.ComboBox {
                 height: textField.height
 
                 colorGroup: PlasmaCore.Theme.ButtonColorGroup
-                source: control.iconRole === "icon" ? control.model.get(control.currentIndex).icon : ''
+                source: {
+                    if (control && control.currentIndex>=0 &&
+                            control.iconRole && control.iconRole === "icon"
+                            && control.model && control.model.get(control.currentIndex)
+                            && control.model.get(control.currentIndex)) {
+
+                        return control.model.get(control.currentIndex).icon;
+                    }
+
+                    return "";
+                }
 
                 visible: source !== ''
             }

shell/package/contents/configuration/pages/BehaviorConfig.qml

@@ -76,6 +76,11 @@ PlasmaComponents.Page {
                 text: screenRow.visible ? i18n("Screen") : i18n("Location")
             }
 
+            Connections {
+                target: universalSettings
+                onScreensCountChanged: screenRow.updateScreens()
+            }
+
             RowLayout {
                 id: screenRow
                 Layout.fillWidth: true