Download improvements

- Use UUID as key in map to help improve access times
- Fix issues with removed/hidden downloads leaving empty rows
- Fix crashes caused by having an empty download list

src/downloadlist.cpp

@@ -241,9 +241,11 @@ void DownloadList::downloadRemoved(QUuid moId)
     log::debug("Download List - Removing Item: {}", downloadIndex);
     emit beginRemoveRows(QModelIndex(), downloadIndex, downloadIndex);
     m_downloadIndexCache.erase(downloadListItem->moId.toString());
-    m_downloadListItems.removeAt(downloadListItem - m_downloadListItems.begin());
+    m_downloadListItems.removeAt(downloadIndex);
+    for (auto item : m_downloadListItems) {
+      m_downloadIndexCache[item.moId.toString()] = m_downloadListItems.indexOf(item);
+    }
     emit endRemoveRows();
-
     log::debug("Download List Size (after remove): {}", m_downloadListItems.size());
   }
 }

src/downloadlistitem.h

@@ -32,6 +32,7 @@ struct DownloadListItem
   ~DownloadListItem()                                  = default;
   DownloadListItem(const DownloadListItem&)            = default;
   DownloadListItem& operator=(const DownloadListItem&) = default;
+  auto operator<=>(const DownloadListItem&) const      = default;
 
   int pendingIndex{-1};
   bool isPending{false};