Fix file pointer position if file was truncated

[rdwebdesign]

What is the problem?

To ensure that the page always displays the most recent lines, the page first finds the end of the log and then starts reading new information from there.
Then while the page is kept open PHP will continue reading the new lines and will update the pointer.

The problem happens when logrotate truncates the file.
The pointer isn't updated and continues at the previous position, but there is no text to read at this position, so nothing is displayed.

The code continues to run without displaying anything until the file exceeds the previous file size (before rotation).

How does this PR solves the problem?

Simple solution:
We need to check if the pointer is beyond the end of the file.
If it is, it means the file has been truncated and we need to read it from the beginning.

What documentation changes (if any) are needed to support this PR?

none

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[yubiuser]

Give me two nights to test this.

[rdwebdesign]

Give me two nights to test this.

If you just want to wait for the log rotation, you can change the cron job to rotate the log every 5 minutes and test it any time.