Fixes matomo-org#6222 silent fail in front of shell_exec to prevent w…

…arnings from breaking the archiver

core/CliMulti/Process.php

@@ -216,7 +216,7 @@ private static function returnsSuccessCode($command)
 
     private static function commandExists($command)
     {
-        $result = shell_exec('which ' . escapeshellarg($command) . ' 2> /dev/null');
+        $result = @shell_exec('which ' . escapeshellarg($command) . ' 2> /dev/null');
 
         return !empty($result);
     }