Fix typo in error message

Signed-off-by: Morris Jobke <hey@morrisjobke.de>

apps/encryption/lib/KeyManager.php

@@ -227,7 +227,7 @@ public function validateMasterKey() {
 			$this->log->error('A private master key is available but the public key could not be found. This should never happen.');
 			return;
 		} elseif (empty($privateMasterKey)) {
-			$this->log->error('A private master key is available but the public key could not be found. This should never happen.');
+			$this->log->error('A public master key is available but the private key could not be found. This should never happen.');
 			return;
 		}