Fix wrong selection on cloning a line down in the editor

(cherry picked from commit 28f74327beca86325cb8f8f9c7926a60ea83c826)

editor/code_editor.cpp

@@ -1261,7 +1261,7 @@ void CodeTextEditor::clone_lines_down() {
 	text_editor->cursor_set_line(cursor_new_line);
 	text_editor->cursor_set_column(cursor_new_column);
 	if (selection_active) {
-		text_editor->select(to_line, to_column, 2 * to_line - from_line, 2 * to_column - from_column);
+		text_editor->select(to_line, to_column, 2 * to_line - from_line, to_line == from_line ? 2 * to_column - from_column : to_column);
 	}
 
 	text_editor->end_complex_operation();