More const detach fixes

src/collection/collectionfilterwidget.cpp

@@ -158,7 +158,7 @@ void CollectionFilterWidget::Init(CollectionModel *model, CollectionFilter *filt
 
   const QList<QAction*> actions = filter_max_ages_.keys();
   for (QAction *action : actions) {
-    int filter_max_age = filter_max_ages_[action];
+    const int filter_max_age = filter_max_ages_.value(action);
     QObject::connect(action, &QAction::triggered, this, [this, filter_max_age]() { model_->SetFilterMaxAge(filter_max_age); } );
   }
 

src/collection/collectionmodel.cpp

@@ -514,7 +514,7 @@ void CollectionModel::AddReAddOrUpdateSongsInternal(const SongList &songs) {
       songs_added << new_song;
       continue;
     }
-    const Song &old_song = song_nodes_[new_song.id()]->metadata;
+    const Song old_song = song_nodes_.value(new_song.id())->metadata;
     bool container_key_changed = false;
     bool has_unique_album_identifier_1 = false;
     bool has_unique_album_identifier_2 = false;
@@ -606,7 +606,7 @@ void CollectionModel::UpdateSongsInternal(const SongList &songs) {
       qLog(Error) << "Song does not exist in model" << new_song.id() << new_song.PrettyTitleWithArtist();
       continue;
     }
-    CollectionItem *item = song_nodes_[new_song.id()];
+    CollectionItem *item = song_nodes_.value(new_song.id());
     const Song &old_song = item->metadata;
     const bool song_title_data_changed = IsSongTitleDataChanged(old_song, new_song);
     const bool art_changed = !old_song.IsArtEqual(new_song);
@@ -648,7 +648,7 @@ void CollectionModel::RemoveSongsInternal(const SongList &songs) {
   for (const Song &song : songs) {
 
     if (song_nodes_.contains(song.id())) {
-      CollectionItem *node = song_nodes_[song.id()];
+      CollectionItem *node = song_nodes_.value(song.id());
 
       if (node->parent != root_) parents << node->parent;
 
@@ -706,7 +706,7 @@ void CollectionModel::RemoveSongsInternal(const SongList &songs) {
     }
 
     // Remove the divider
-    int row = divider_nodes_[divider_key]->row;
+    const int row = divider_nodes_.value(divider_key)->row;
     beginRemoveRows(ItemToIndex(root_), row, row);
     root_->Delete(row);
     endRemoveRows();

src/collection/collectionview.cpp

@@ -611,7 +611,7 @@ void CollectionView::SearchForThis() {
       CollectionItem *item = app_->collection_model()->IndexToItem(index);
       const CollectionModel::GroupBy group_by = app_->collection_model()->GetGroupBy()[item->container_level];
       while (!item->children.isEmpty()) {
-        item = item->children.first();
+        item = item->children.constFirst();
       }
 
       switch (group_by) {

src/collection/collectionwatcher.cpp

@@ -1131,7 +1131,7 @@ void CollectionWatcher::RescanPathsNow() {
     if (stop_or_abort_requested()) break;
     ScanTransaction transaction(this, dir, false, false, mark_songs_unavailable_);
 
-    const QStringList paths = rescan_queue_[dir];
+    const QStringList paths = rescan_queue_.value(dir);
 
     QMap<QString, quint64> subdir_files_count;
     for (const QString &path : paths) {