[m.i877] Disconnect mask items properly (#877) ()

Merging branch 'm.i877'  into 'main'.

See merge request !2213

GUI/View/Setup/MaskEditorToolpanel.cpp

@@ -139,7 +139,7 @@ void MaskEditorToolpanel::onCustomContextMenuRequested(const QPoint& point)
 void MaskEditorToolpanel::setCurrentMaskItem(MaskItem* maskItem)
 {
     if (m_currentMaskItem)
-        disconnect(m_currentMaskItem, nullptr, this, nullptr);
+        disconnect(m_currentMaskItem, nullptr, nullptr, nullptr);
 
     GUI::Util::Layout::clearLayout(m_editor_layout);