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/Content/OEmbed.php

@@ -108,7 +108,7 @@ class OEmbed
 				$txt = '{"type":"error"}';
 			} else { //save in cache
 				$j = json_decode($txt);
-				if ($j->type != "error") {
+				if (!empty($j->type) && $j->type != "error") {
 					dba::insert('oembed', [
 						'url' => normalise_link($embedurl),
 						'maxwidth' => $a->videowidth,