[netinstall] Missing initialisations, split out slot

- m_queue was not initialized to nullptr, crashes
- split queue-is-done to a separate slot rather than a lambda
- prefer queueing calls to fetchNext(), for responsiveness

src/modules/netinstall/Config.cpp

@@ -93,6 +93,17 @@ Config::loadGroupList( const QVariantList& groupData )
     emit statusReady();
 }
 
+void
+Config::loadingDone()
+{
+    if ( m_queue )
+    {
+        m_queue->deleteLater();
+        m_queue = nullptr;
+    }
+}
+
+
 void
 Config::setConfigurationMap( const QVariantMap& configurationMap )
 {
@@ -133,11 +144,8 @@ Config::setConfigurationMap( const QVariantMap& configurationMap )
     }
     if ( m_queue )
     {
-        connect( m_queue, &LoaderQueue::done, [this]() {
-            m_queue->deleteLater();
-            m_queue = nullptr;
-        } );
-        m_queue->fetchNext();
+        connect( m_queue, &LoaderQueue::done, this, &Config::loadingDone );
+        QMetaObject::invokeMethod( m_queue, "fetchNext", Qt::QueuedConnection );
     }
 }
 

src/modules/netinstall/Config.h

@@ -83,12 +83,13 @@ Q_SIGNALS:
 
 private Q_SLOTS:
     void retranslate();
+    void loadingDone();
 
 private:
     CalamaresUtils::Locale::TranslatedString* m_sidebarLabel = nullptr;  // As it appears in the sidebar
     CalamaresUtils::Locale::TranslatedString* m_titleLabel = nullptr;
     PackageModel* m_model = nullptr;
-    LoaderQueue* m_queue;
+    LoaderQueue* m_queue = nullptr;
     Status m_status = Status::Ok;
     bool m_required = false;
 };

src/modules/netinstall/LoaderQueue.cpp

@@ -95,6 +95,12 @@ LoaderQueue::fetch( const QUrl& url )
     }
 }
 
+/** @brief Call fetchNext() on the queue if it can
+ *
+ * On destruction, a new call to fetchNext() is queued, so that
+ * the queue continues loading. Calling release() before the
+ * destructor skips the fetchNext(), ending the queue-loading.
+ */
 class FetchNextUnless
 {
 public: