Unsafe casting in Add_Entry

[xezon]

int Add_Entry(Utf16String *string, int color, int row, int column, GameWindow *list_box, bool overwrite)
{
    _ListboxData *data = static_cast<_ListboxData *>(list_box->Win_Get_User_Data());

    if (column < data->m_columns && row < data->m_listLength) {
        if (row == -1) {
            row = data->m_insertPos++;
            data->m_endPos++;
        }

        if (column == -1) {
            column = 0;
        }

        int wrap = data->m_columnWidth[column] - 7;
        int adjust = 0;
        _ListEntryRow *list_row = &data->m_listData[row];

        if (list_row->m_cell != nullptr) {
            if (!overwrite) {
                Move_Rows_Down(data, row);
                list_row->m_cell = new _ListEntryCell[data->m_columns];
                memset(list_row->m_cell, 0, sizeof(_ListEntryCell) * data->m_columns);
                adjust = 1;
            }
        } else {
            list_row->m_cell = new _ListEntryCell[data->m_columns];
            memset(list_row->m_cell, 0, sizeof(_ListEntryCell) * data->m_columns);
            adjust = 1;
        }

        list_row->m_cell[column].m_cellType = LISTBOX_TEXT;
        list_row->m_cell[column].m_textColor = color;

        if (list_row->m_cell[column].m_data == nullptr) {
            list_row->m_cell[column].m_data = g_theDisplayStringManager->New_Display_String();
        }

        DisplayString *text = static_cast<DisplayString *>(list_row->m_cell[column].m_data);

This function allocates a DisplayString for list_row->m_cell[column].m_data if it is null, but if it is not null, then is there a guarantee that list_row->m_cell[column].m_data is actually pointing to a DisplayString?

What if this was a LISTBOX_IMAGE before and m_data is actually not a DisplayString?

To be safe, there needs to be this check before:

if (list_row->m_cell[column].m_data != nullptr && list_row->m_cell[column].m_cellType == LISTBOX_TEXT) {
  g_theDisplayStringManager->Free_Display_String(static_cast<DisplayString *>(list_row->m_cell[column].m_data));
  list_row->m_cell[column].m_data = nullptr;
}