handle zero-length case in reshape_bits()

src/parsers/bits.c

@@ -29,7 +29,7 @@ static HParsedToken *reshape_bits(const HParseResult *p, void* signedp_p) {
   HParsedToken *ret = h_arena_malloc(p->arena, sizeof(HParsedToken));
   ret->token_type = TT_UINT;
 
-  if(signedp && (seq->elements[0]->uint & 128))
+  if(signedp && seq->used > 0 && (seq->elements[0]->uint & 128))
     ret->uint = -1; // all ones
 
   for(size_t i=0; i<seq->used; i++) {