ext.js存储记录未定义

var debtProtectionId = 0
    // get the selected id of debt protection dropdown
    if (mainPanel.generalPanel.calculationsFieldSet.debtProtection.getValue() != '') {
        debtProtectionId = mainPanel.generalPanel.calculationsFieldSet.debtProtection.getValue();
    }
    // get the store record with this id
    var storeRecord = planCombinationsStore.getAt(debtProtectionId)

当我运行代码时,它说“storerecord is undefined”。

这可能是什么原因?