--- a/src/frontend.c	Thu Jul 11 20:05:26 2024 +0200
+++ b/src/frontend.c	Thu Jul 11 20:13:59 2024 +0200
@@ -44,6 +44,7 @@
 } Settings;
 
 static int appendfile(const char *filename, FILE *fout, const char *errmsg) {
+    if (filename == NULL) return 0; // nothing to append
     FILE *fin = fopen(filename, "r");
     if (!fin) {
         perror(errmsg);