[qtgrilo] Fix crash on callback for cancelled operation. JB#63255

GriloDatasource dtor cancels the ongoing query but the callback
gets triggered anyway with cancelled status. Avoid referencing
the already deleted instance.

Regression on commit cf32174, the id is already cleared on cancel
so guess this one got into wrong error handling branch.

Author: pvuorela

Diff for: declarative/griloplugin.cpp

@@ -40,7 +40,6 @@ GriloPlugin::GriloPlugin(QObject *parent)
 
 GriloPlugin::~GriloPlugin()
 {
-
 }
 
 void GriloPlugin::registerTypes(const char *uri)

Diff for: src/grilodatasource.cpp

@@ -388,14 +388,14 @@ void GriloDataSource::grilo_source_result_cb(GrlSource *source, guint op_id,
     Q_UNUSED(source)
     GriloDataSource *that = static_cast<GriloDataSource *>(user_data);
 
-    // We get an error if the operation has been canceled:
+    // We get an error if the operation has been cancelled:
     if (error) {
         if (error->domain != GRL_CORE_ERROR || error->code != GRL_CORE_ERROR_OPERATION_CANCELLED) {
             // TODO: error reporting?
             qCritical() << "Operation failed" << error->message;
-        } else {
-            // Cancelled operation notification. Nothing else to be done.
             that->d->m_previouslyAddedId.clear();
+        } else {
+            // Cancelled operation notification. Nothing else to be done and the instance might be deleted already
             return;
         }
     }