Merge branch 'trade' into 'master'

Fix regression #5666

Closes #5666

See merge request OpenMW/openmw!382

apps/openmw/mwgui/tradewindow.cpp

@@ -519,6 +519,9 @@ namespace MWGui
 
     void TradeWindow::onClose()
     {
+        // Make sure the window was actually closed and not temporarily hidden.
+        if (MWBase::Environment::get().getWindowManager()->containsMode(GM_Barter))
+            return;
         resetReference();
     }
 }