Fix macOS redraw crash after closing merge details

Sometimes, if the underlying PO file changed a lot, implicit redraw of
the list control upon closing merge details would crash (referencing no
longer existing CatalogItems).

This doesn't have w/o showing the details because then the redraw would
only happen after m_catalog was updated.

Author: vslavik

src/edframe.cpp

@@ -1583,6 +1583,7 @@ void PoeditFrame::UpdateCatalog(const wxString& pot_file)
     // This ensures that the list control won't be redrawn during Update()
     // call when a dialog box is hidden; another alternative would be to call
     // m_list->CatalogChanged(NULL) here
+    // *or* to make sure PerformUpdateFromXXX() always returns a new Catalog instance
     std::shared_ptr<wxWindowUpdateLocker> locker;
     if (m_list)
         locker.reset(new wxWindowUpdateLocker(m_list));
@@ -1617,7 +1618,7 @@ void PoeditFrame::UpdateCatalog(const wxString& pot_file)
         bg_work = PerformUpdateFromReferenceWithUI(this, m_catalog, pot_file);
     }
 
-    bg_work.then_on_main([=](CatalogPtr updated_catalog)
+    bg_work.then_on_main([this,locker](CatalogPtr updated_catalog)
     {
         if (!updated_catalog)
             return;
@@ -1636,6 +1637,8 @@ void PoeditFrame::UpdateCatalog(const wxString& pot_file)
                 RefreshControls();
             });
         }
+
+        // locker gets released now and the list is redrawn
     });
 }