diff -r 2837b549e616 -r 94b0a30a1886 src/model.h
--- a/src/model.h	Wed Jun 22 16:53:35 2022 +0300
+++ b/src/model.h	Wed Jun 22 20:10:57 2022 +0300
@@ -220,7 +220,7 @@
 	const ModelElement& at(std::size_t position) const;
 	ModelId idAt(std::size_t position) const;
 	void assignAt(std::size_t position, const ModelElement& element);
-	std::optional<int> find(ModelId id) const;
+	std::optional<std::size_t> find(ModelId id) const;
 	void remove(std::size_t index);
 	int rowCount(const QModelIndex&) const override;
 	QVariant data(const QModelIndex& index, int role) const override;