Several more warnings ... (#5340)

* Some more warnings removed

* Even more warnings ...

* Will it ever end? ;-)

* Avoid warning in dbstructure

* Origin and OStatus ...

* There are more warnings solved ... yeah!

* And again ...

* We are not done yet

* And more ...

* And some new places ...

* And more in the feeds

* Avoid some more

* And some backend stuff

* Notifications cleared

* Some more stuff

* and again ...

* It's getting fewer ...

* Some warnings had been hidden in the notifications

* Fix the fix

* And another missing one ...

* We need the owner here, not the user

* Forgotten user

* And more ...

* And some more warnings disappeared ...

* Some more frontend warnings

* Some backend warnings removed

* Fixed sidebar for "vier"

* And more ...

* Some more ...

* And something for "remote self"

* Am I stuck in an endless loop?

* Fix: Clear tag and file field on update

* Preset page content

src/Module/Login.php

@@ -248,7 +248,7 @@ class Login extends BaseModule
 				// Make sure to refresh the last login time for the user if the user
 				// stays logged in for a long time, e.g. with "Remember Me"
 				$login_refresh = false;
-				if (!x($_SESSION['last_login_date'])) {
+				if (empty($_SESSION['last_login_date'])) {
 					$_SESSION['last_login_date'] = DateTimeFormat::utcNow();
 				}
 				if (strcmp(DateTimeFormat::utc('now - 12 hours'), $_SESSION['last_login_date']) > 0) {