TypeError in Asset::lastModified() when last_modified meta is null

[v-Woody]

Bug Description

Asset::lastModified() throws a TypeError when the last_modified meta value is null. This can happen when an asset's meta cache does not contain a last_modified entry (e.g. the file was uploaded without metadata being fully generated, or the meta cache is stale/incomplete).

Exception

TypeError: Carbon\Carbon::createFromTimestamp(): Argument #1 ($timestamp) must be of type string|int|float, null given

File: src/Assets/Asset.php:604

Stack Trace

Carbon\Carbon::createFromTimestamp() at vendor/nesbot/carbon/src/Carbon/Traits/Timestamp.php:30
Statamic\Assets\Asset->lastModified() at vendor/statamic/cms/src/Assets/Asset.php:604

Steps to Reproduce

1. Have an asset container with files
2. If a file's meta YAML does not include last_modified (e.g. incomplete meta generation)
3. Browse the asset container in the Control Panel
4. The CP returns a 500 error

Expected Behavior

lastModified() should gracefully handle a null value and fall back to a sensible default (e.g. epoch 0) instead of throwing a TypeError.

Environment

• Statamic: v6.14.0
• PHP: 8.5
• Laravel: 13