【AWS:Lambda】CloudWatchに毎回エラーが出てしまう。

#初心者マークで失礼致します。
#エラーの原因を知りたい
CloudWatchのログにて、一部のJavaScriptのエラーが毎回吐き出されるので、このエラーの原因を知りたいです。
####エラー文

CloudWatch
1message: 'parseEvent() received invalid SES message:',
2level: 'error',
3---------------------------------------------------------
4{ level: 'error',
5message: 'Step returned error: Error: Received invalid SES message.',
6error: Error: Error: Received invalid SES message.
7at exports.parseEvent (/var/task/index.js:59:27)
8at <anonymous>,
9stack: 'Error: Error: Received invalid SES message.\n at exports.parseEvent (/var/task/index.js:59:27)\n at <anonymous>' }
10---------------------------------------------------------
11{
12    "errorMessage": "Error: Step returned error.",
13    "errorType": "Error",
14    "stackTrace": [
15        "/var/task/index.js:310:28",
16        "<anonymous>"
17    ]
18}

#Lambdaに記述するJavaScriptの一部

JavaScript
1/**
2 * Parses the SES event record provided for the `mail` and `receipients` data.
3 *
4 * @param {object} data - Data bundle with context, email, etc.
5 *
6 * @return {object} - Promise resolved with data.
7 */
8exports.parseEvent = function(data) {
9  // Validate characteristics of a SES event record.
10  if (!data.event ||
11      !data.event.hasOwnProperty('Records') ||
12      data.event.Records.length !== 1 ||
13      !data.event.Records[0].hasOwnProperty('eventSource') ||
14      data.event.Records[0].eventSource !== 'aws:ses' ||
15      data.event.Records[0].eventVersion !== '1.0') {
16    data.log({message: "parseEvent() received invalid SES message:",
17      level: "error", event: JSON.stringify(data.event)});
18    return Promise.reject(new Error('Error: Received invalid SES message.'));
19  }
20
21  data.email = data.event.Records[0].ses.mail;
22  data.recipients = data.event.Records[0].ses.receipt.recipients;
23  return Promise.resolve(data);
24};