Merge pull request #1358 from 0xbsec/master

Fix overflow in mangle_dupechar_last function

src/rp_kernel_on_cpu.c

@@ -528,6 +528,7 @@ static int mangle_dupechar_last (MAYBE_UNUSED const u8 p0, MAYBE_UNUSED const u8
 {
   const int out_len = len + p0;
 
+  if (len     ==                0) return (len);
   if (out_len >= RP_PASSWORD_SIZE) return (len);
 
   const u8 c = buf[len - 1];