Commit d6a18a7738 for php.net

commit d6a18a773899d07750b30082b5f5ce36aa3c70df
Author: Nikita Popov <nikita.ppv@gmail.com>
Date:   Fri Oct 16 18:38:03 2020 +0200

    Properly handle NULL output start filename

diff --git a/main/output.c b/main/output.c
index cffadede80..d155123834 100644
--- a/main/output.c
+++ b/main/output.c
@@ -758,7 +758,7 @@ PHPAPI void php_output_set_implicit_flush(int flush)
  * Get the file name where output has started */
 PHPAPI const char *php_output_get_start_filename(void)
 {
-	return ZSTR_VAL(OG(output_start_filename_str));
+	return OG(output_start_filename_str) ? ZSTR_VAL(OG(output_start_filename_str)) : NULL;
 }
 /* }}} */