Add null guards in AppletHost and TaskWidget

AppletHost: setPreloadFullRepresentation(true) does not guarantee
fullRepresentationItem() is non-null on return — the applet loads
asynchronously. Wire a single-shot connection to
fullRepresentationItemChanged to emit appletReady() when the item
arrives.

TaskWidget: operationDescription() can return null for an unknown
operation name; bail out rather than dereferencing it.

components/mobileshell/components/applethost.cpp

@@ -91,7 +91,18 @@ QQuickItem *AppletHost::fullRepresentationFor(const QString &pluginId)
 
     item->setPreloadFullRepresentation(true);
 
-    return item->fullRepresentationItem();
+    auto *fullRepItem = item->fullRepresentationItem();
+    if (!fullRepItem) {
+        connect(
+            item,
+            &PlasmaQuick::AppletQuickItem::fullRepresentationItemChanged,
+            this,
+            [this, pluginId]() {
+                Q_EMIT appletReady(pluginId);
+            },
+            static_cast<Qt::ConnectionType>(Qt::AutoConnection | Qt::SingleShotConnection));
+    }
+    return fullRepItem;
 }
 
 #include "applethost.moc"

components/mobileshell/components/applethost.h

@@ -32,6 +32,9 @@ public:
 
     Q_INVOKABLE QQuickItem *fullRepresentationFor(const QString &pluginId);
 
+Q_SIGNALS:
+    void appletReady(const QString &pluginId);
+
 private:
     void ensureCorona();
 

components/mobileshell/qml/statusbar/TaskWidget.qml

@@ -50,6 +50,9 @@ Item {
 
             var operationName = mouse.button === Qt.RightButton ? "ContextMenu" : "Activate";
             var operation = model.service.operationDescription(operationName);
+            if (!operation) {
+                return;
+            }
             operation.x = taskIcon.mapToGlobal(0, 0).x;
             operation.y = taskIcon.mapToGlobal(0, taskIcon.height).y;
             model.service.startOperationCall(operation);