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

boot.php

@@ -866,7 +866,7 @@ function goaway($path)
  */
 function local_user()
 {
-	if (x($_SESSION, 'authenticated') && x($_SESSION, 'uid')) {
+	if (!empty($_SESSION['authenticated']) && !empty($_SESSION['uid'])) {
 		return intval($_SESSION['uid']);
 	}
 	return false;
@@ -909,6 +909,11 @@ function remote_user()
 //	if (local_user()) {
 //		return false;
 //	}
+
+	if (empty($_SESSION)) {
+		return false;
+	}
+
 	if (x($_SESSION, 'authenticated') && x($_SESSION, 'visitor_id')) {
 		return intval($_SESSION['visitor_id']);
 	}