Fix some PHP8.1 issues if possible

src/App/Page.php

@@ -130,7 +130,7 @@ class Page implements ArrayAccess
 	 * The return value will be casted to boolean if non-boolean was returned.
 	 * @since 5.0.0
 	 */
-	public function offsetExists($offset)
+	public function offsetExists($offset): bool
 	{
 		return isset($this->page[$offset]);
 	}

src/Core/L10n.php

@@ -188,10 +188,10 @@ class L10n
 	{
 		$lang_variable = $server['HTTP_ACCEPT_LANGUAGE'] ?? null;
 
-		$acceptedLanguages = preg_split('/,\s*/', $lang_variable);
-
-		if (empty($acceptedLanguages)) {
+		if (empty($lang_variable)) {
 			$acceptedLanguages = [];
+		} else {
+			$acceptedLanguages = preg_split('/,\s*/', $lang_variable);
 		}
 
 		// Add get as absolute quality accepted language (except this language isn't valid)

src/Util/Network.php

@@ -485,11 +485,11 @@ class Network
 						$get('host') .
 						($port ? ":$port" : '');
 
-		return	(strlen($scheme) ? $scheme . ':' : '') .
-			(strlen($authority) ? '//' . $authority : '') .
+		return	(!empty($scheme) ? $scheme . ':' : '') .
+			(!empty($authority) ? '//' . $authority : '') .
 			$get('path') .
-			(strlen($query) ? '?' . $query : '') .
-			(strlen($fragment) ? '#' . $fragment : '');
+			(!empty($query) ? '?' . $query : '') .
+			(!empty($fragment) ? '#' . $fragment : '');
 	}
 
 	/**

src/Util/ReversedFileReader.php

@@ -60,7 +60,7 @@ class ReversedFileReader implements \Iterator
 		$this->fh = fopen($filename, 'r');
 		if (!$this->fh) {
 			// this should use a custom exception.
-			throw \Exception("Unable to open $filename");
+			throw new \Exception("Unable to open $filename");
 		}
 		$this->filesize = filesize($filename);
 		$this->pos      = -1;