refstr: handle NULL in refstr[n]dup()

diff --git a/com32/menu/refstr.c b/com32/menu/refstr.c
index 413561c..8b4c718 100644 (file)
--- a/com32/menu/refstr.c
+++ b/com32/menu/refstr.c
@@ -25,6 +25,9 @@ const char *refstrndup(const char *str, size_t len)
 {
   char *r;
 
+  if (!str)
+    return NULL;
+
   len = strnlen(str, len);
   r = malloc(sizeof(unsigned int)+len+1);
   *(unsigned int *)r = 1;
@@ -39,6 +42,9 @@ const char *refstrdup(const char *str)
   char *r;
   size_t len;
 
+  if (!str)
+    return NULL;
+
   len = strlen(str);
   r = malloc(sizeof(unsigned int)+len+1);
   *(unsigned int *)r = 1;