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/Protocol/Diaspora.php

@@ -3352,12 +3352,12 @@ class Diaspora
 
 		$guid = "";
 		preg_match("/guid='(.*?)'/ism", $attributes, $matches);
-		if ($matches[1] != "") {
+		if (!empty($matches[1])) {
 			$guid = $matches[1];
 		}
 
 		preg_match('/guid="(.*?)"/ism', $attributes, $matches);
-		if ($matches[1] != "") {
+		if (!empty($matches[1])) {
 			$guid = $matches[1];
 		}
 
@@ -3382,12 +3382,12 @@ class Diaspora
 
 		$profile = "";
 		preg_match("/profile='(.*?)'/ism", $attributes, $matches);
-		if ($matches[1] != "") {
+		if (!empty($matches[1])) {
 			$profile = $matches[1];
 		}
 
 		preg_match('/profile="(.*?)"/ism', $attributes, $matches);
-		if ($matches[1] != "") {
+		if (!empty($matches[1])) {
 			$profile = $matches[1];
 		}