主题：打开窗体报错

我在入库窗体的 AfterLoad事件中写了如下代码，如果数据库中的数据时空时运行窗体时报一下错误怎么处理呀？

Dim cmb As WinForm.ComboBox =  Forms("POS机批量入库窗体").Controls("suoshucangkuCombo")
cmb.ComboList = DataTables("仓库资料").GetComboListString("仓库名称")
cmb.SelectedIndex = 1
cmb= Forms("POS机批量入库窗体").Controls("jijuxinghaoCombo")
cmb.ComboList = DataTables("pos机信息表").GetComboListString("机具型号")
cmb.SelectedIndex = 1
cmb = Forms("POS机批量入库窗体").Controls("changjiamingchengCombo")
cmb.ComboList = DataTables("POS机信息表").GetComboListString("厂家名称")
cmb.SelectedIndex = 5