Pull Request resolves #47944

• I read the Generative AI policy and my contribution is either not created with the help of AI or is compatible with the policy and GNU/GPL 2 or later.

Summary of Changes

The "Running since" tooltip ( in Scheduled Tasks page) for a locked task was incorrectly attempting to format $item->last_execution instead of $item->locked. Because a task crashing on its first run has a NULL value for last_execution, passing it to the date formatter caused PHP to crash.
This PR swaps $item->last_execution with $item->locked which logically represents the start time of the current run and is guaranteed to not be NULL within that code block.

Testing Instructions

1. Navigate to System -> Scheduled Tasks.
2. Click New to create a new task , save and close without running it.
3. Access your database manager and locate the newly created task in the #__scheduler_tasks table.
4. Manually edit the row: Set the locked column to a valid datetime and ensure last_execution remains NULL.
5. Return to the Joomla Administrator and refresh the Scheduled Tasks page.

Actual result BEFORE applying this Pull Request

The Scheduled Tasks list fails to load properly and displays an uncaught error message.

Expected result AFTER applying this Pull Request

The Scheduled Tasks list loads properly. The stuck task correctly displays the 'running man' icon, and hovering over it displays the accurate tooltip

Link to documentations

Please select:

• Documentation link for guide.joomla.org:

• No documentation changes for guide.joomla.org needed

• Pull Request link for manual.joomla.org:

• No documentation changes for manual.joomla.org needed