fix(baseN): decode: empty string case

src/baseN.cpp

@@ -99,11 +99,12 @@ namespace baseN
         std::span<uint8_t> dv(data, data_size);
         auto sv_it = sv.begin();
         auto quo_it = dv.rbegin();
-        auto quo_it_last = dv.rbegin() + 1;
+        auto quo_it_last = dv.rbegin();
         uint16_t div;
 
         if (sv.size() != 0)
         {
+            quo_it_last++;
             *quo_it = map[(int8_t)*sv_it++];
             while (sv_it < sv.end())
             {

test/test-baseN.cpp

@@ -41,6 +41,7 @@ std::vector<std::pair<std::string, std::string>> tests = {
     {"KyKX", "387ae2"},
     {"KyKXa", "0ccbd755"},
     {"KyKXaa", "02e62ec963"},
+    {"111KyKX", "000000387ae2"},
     {"4uqWDRyJZUpS6KKwLAiitndmv7TPFt2bfxVVfhJhgTn3Rh6aQtGHQY6PhhNDpCwSNU8a",
      "057902f9cebebb68879911002aae743280140a78c4a077405b057902f9cebebb68879911002aae743280140a78c4a077405b"},
 };