Fix a possible crash with the remove all files dialog

changelog/unreleased/8314

@@ -0,0 +1,6 @@
+Bugfix: Fix potential crashes with the remove all dialog
+
+We fixed a bug a dialog window belonging to a removed account could still
+be visible. User action on that dialog would then cause a crash.
+
+https://github.com/owncloud/client/pull/8314

src/gui/folder.cpp

@@ -1223,6 +1223,7 @@ void Folder::slotAboutToRemoveAllFiles(SyncFileItem::Direction dir, std::functio
         }
         setSyncPaused(oldPaused);
     });
+    connect(this, &Folder::destroyed, msgBox, &QMessageBox::deleteLater);
     msgBox->open();
 }
 

src/libsync/syncengine.cpp

@@ -732,10 +732,11 @@ void SyncEngine::slotDiscoveryFinished()
         }
 
         QPointer<QObject> guard = new QObject();
-        auto callback = [this, finish, guard](bool cancel) -> void {
+        QPointer<QObject> self = this;
+        auto callback = [this, self, finish, guard](bool cancel) -> void {
             // use a guard to ensure its only called once...
-            if (!guard)
-            {
+            // qpointer to self to ensure we still exist
+            if (!guard || !self) {
                 return;
             }
             guard->deleteLater();