fixed $this in static methods

application/core/Files/BackupUtil.php

@@ -101,7 +101,7 @@ abstract class BackupUtil {
 			}
 			if (is_dir($filePath)) {
 				$zipArchive->addEmptyDir($localPath);
-				$this->zipDirectory($zipArchive, $filePath, $prefixLength, $excludes);
+				self::zipDirectory($zipArchive, $filePath, $prefixLength, $excludes);
 				continue;
 			}
 		}

application/core/Files/FileUtil.php

@@ -143,7 +143,7 @@ abstract class FileUtil {
 				}
 				if (!is_writable($fileName)) {
 					$message = "Write-Access missing for File '{$fileName}'!";
-					$this->maniaControl->log($message);
+					logMessage($message);
 					return false;
 				}
 			}