Fix bug kh_put after kh_del report by @mirichi

include/mruby/khash.h

@@ -188,7 +188,7 @@ kh_fill_flags(uint8_t *p, uint8_t c, size_t len)
     if (del_k != kh_end(h)) {                                           \
       /* put at del */                                                  \
       h->keys[del_k] = key;                                             \
-      h->ed_flags[k/4] &= ~__m_del[k%4];                                \
+      h->ed_flags[del_k/4] &= ~__m_del[del_k%4];                        \
       h->size++;                                                        \
     }                                                                   \
     else {                                                              \