Merge pull request #4812 from LibreSign/fix/prevent-error-when-pdfsig-output-is-empty

fix: prevent error when output of pdfsig is empty

Author: samuelsonbrito

lib/Handler/Pkcs12Handler.php

@@ -202,6 +202,9 @@ private function popplerUtilsPdfSignFallback($resource, int $signerCounter): arr
 		file_put_contents($tempFile, $content);
 
 		$content = shell_exec('pdfsig ' . $tempFile);
+		if (empty($content)) {
+			return [];
+		}
 		$lines = explode("\n", $content);
 
 		$lastSignature = 0;