fix PHP 8.0 warnings

[madu696]

Using phpBB 3.3.4 and PHP 8.0 I have noticed so far 2 warnings.

[phpBB Debug] PHP Warning: in file [ROOT]/ext/tas2580/seourls/event/listener.php on line 439: Undefined array key "post_id" #69 (when there is no posts in topic)

[phpBB Debug] PHP Warning: in file [ROOT]/ext/tas2580/seourls/event/listener.php on line 245 and 246 Undefined array key "active_f_row" and Undefined array key "active_t_row" + Trying to access array offset on value of type bool/null (when new user has no post/topic).

[zetrader]

This fix works fine with phpbb 3.3.4 and php 8.0.12

[zetrader]

I've tried with phpbb 3.3.7 and php 8.1.5, the fix still works fine.

[zetrader]

It works but i've noticed something that didn't happen before with php 8.0 or 8.1, when there is a second page for a topic, the link becomes :
my-topic.html?start=10 instead of my-topic.html-s10.html, and then if we click on the first page, the link is now viewtopic.php?t=x like there's no rewrite, but in source code, the canonical url is still my-topic.html.
Any way to fix this?

EDIT : i've tried without fix, phpbb 3.3.8 and php 8.1 it's the same bug, so the fix is not the problem, i guess the script has a new pagination problem of the topics with php 8.0 and php 8.1