Only call toString on id if truthy in getNavigateTxData()

Author: danjm

ui/app/pages/confirm-transaction-base/confirm-transaction-base.component.js

@@ -467,7 +467,7 @@ export default class ConfirmTransactionBase extends Component {
   getNavigateTxData () {
     const { currentNetworkUnapprovedTxs, txData: { id } = {} } = this.props
     const enumUnapprovedTxs = Object.keys(currentNetworkUnapprovedTxs).reverse()
-    const currentPosition = enumUnapprovedTxs.indexOf(id.toString())
+    const currentPosition = enumUnapprovedTxs.indexOf(id ? id.toString() : '')
 
     return {
       totalTx: enumUnapprovedTxs.length,