I have been trying to add a feature to a website that allows users to input an icalender link and will display it on the website. I found that the feature works when I input the link manually into DynamoDB. However the when I invoke the lambda function to add the link to the DB it throws this error and the DynamoDB never updates:

TypeError: Cannot read properties of undefined (reading '0'),
                at e.visit (/var/task/calendar/put_ical.js:255:30795),
                at serializeAws_json1_0AttributeValue (/var/task/calendar/put_ical.js:255:150114),
                at /var/task/calendar/put_ical.js:255:174402,
                at Array.reduce (<anonymous>),
                at serializeAws_json1_0MapAttributeValue (/var/task/calendar/put_ical.js:255:174313),
                at Object.M (/var/task/calendar/put_ical.js:255:150291),
                at e.visit (/var/task/calendar/put_ical.js:255:30690),
                at serializeAws_json1_0AttributeValue (/var/task/calendar/put_ical.js:255:150114),
                at /var/task/calendar/put_ical.js:255:171557,
                at Array.map (<anonymous>)

Here is the snippet of code I believe is throwing this error:

export const main = async (event) => {
  try {
    //Parse parameters and create ical id
    const id = randomUUID();
    const {skill_id, url} = JSON.parse(event.body);

    //Update DynamoDB with new ical
    const update = {
      TableName: "Skill_Info",
      Key: { skill_id: { S: skill_id } },
      UpdateExpression: "SET ical = list_append(:i)",
      ExpressionAttributeValues: {
        ":i": { M: { id: { S: id }, url: { S: url } } }
      },
    };
    await updateDynamoItem(update);

And here is the way the function is getting invoked:

return useMutation({
    mutationFn: (params) =>
      API.post("api", "put_ical", {
        body: {
          skill_id: userData.skill_id,
          url: params.url
        },
      }),

The ical attribute in the DB starts as a empty list and never gets updated. I honestly have no I idea why this is happening.