Describe the bug

When calling filter_log_events using CloudWatchLogs client, the nextToken key is always coming with a token instead of null even though there are no results.

Expected Behavior

nextToken should be null when events is empty.

Current Behavior

events returns an empty list but nextToken is not null

Reproduction Steps

1. Create a CloudWatchLogs client
2. Call filter_log_events with logGroupName, filterPattern, startTime, endTime
3. Iterate over pages with the nextToken.

Possible Solution

I don't have a possible solution but a workaround could be to also check the results if that is empty, just ignore the nextToken

Additional Information/Context

The odd thing is that this is only happening with one AWS account so far.

To do the filtering, we first call describe_log_groups to get the list of log groups and then perform the filtering for each group.

Here are the some of the arguments I used:

startTime = 1724946563020
endTime = 1725551363020
filterPattern = '{$.readOnly = false && ($.eventName = "CreateAccessKey" || $.eventName = "DeleteAccessKey" || $.eventName = "UpdateAccessKey" || $.eventName = "CreateLoginProfile" || $.eventName = "UpdateLoginProfile" || $.eventName = "DeleteLoginProfile" || $.eventName = "CreatePolicy" || $.eventName = "DeletePolicy" || $.eventName = "AttachUserPolicy" || $.eventName = "DetachUserPolicy" || $.eventName = "AttachGroupPolicy" || $.eventName = "DetachGroupPolicy" || $.eventName = "AttachRolePolicy" || $.eventName = "DetachRolePolicy" || $.eventName = "PutUserPolicy" || $.eventName = "DeleteUserPolicy" || $.eventName = "PutGroupPolicy" || $.eventName = "DeleteGroupPolicy" || $.eventName = "PutRolePolicy" || $.eventName = "DeleteRolePolicy")}'
logGroupName = 'aws-cloudtrail-logs-us'

And here some actual responses from the filter_log_events

First call

{
    'events': [],
    'searchedLogStreams': [],
    'nextToken': 'Bxkq6kVGFtq2y_MoigeqscPOdhXVbhiVtLoAmXb5jCo-J4ub4atWFi6pePqNs7mRKkYCSSs9IimWr8Xi7GBPMaUH88oHH_P8Wu9fW7nHndM7aRAIAgrkh0Lp-O9Y4FX3e2GN7q4cuKB97nMXpl5EpWbIsPOF5kwHGwIH8PTizyX4h0Gay8fTxQ2Xmd4HcPw7foC7QRm4npaaSjuyyQWnsBzb0KmS8F3RE_e8TZIpfaoF5B4jzeU0utoThPxTLaqS81MqmKYtqQLOWA-QGD1xNw',
    'ResponseMetadata': {
        'RequestId': '29daab62-8be4-4d02-997f-435d7c21cdff',
        'HTTPStatusCode': 200,
        'HTTPHeaders': {...},
        'RetryAttempts': 0,
    },
}

Second call

{
    'events': [],
    'searchedLogStreams': [],
    'nextToken': 'Bxkq6kVGFtq2y_MoigeqscPOdhXVbhiVtLoAmXb5jCojwBgZEf6LNx1087xbbrYSh9yQVDcRp0Q1KWq2KS92-zCrMPMoJ5OQezrUspC_T42pPEsvHmxc3TwOAdIuacjnipZWfZNseUTWEBd5fL4tOt3WSDov9XUT3_iscd23BFEutBi88IzZG09WVGfoYPTKWgQ1EsZyKpdqm5se-w26iUE5OeeHXTmlwY9hmVKwgd7aMEyvUQEGPufQOHAyhaNjxDebszWs5h28UyfmAuKi-Q',
    'ResponseMetadata': {
        'RequestId': 'f24a9577-4bc8-4303-9b65-dc2d3ed57ab5',
        'HTTPStatusCode': 200,
        'HTTPHeaders': {...},
        'RetryAttempts': 0,
    },
}

SDK version used

boto3==1.34.80

Environment details (OS name and version, etc.)

MacOS Sonoma 14.6.1 (23G93), Ubuntu 22.04 docker image