Merge pull request #202 from nielsdos/fix

Fix #200: Segmentation fault merging keys of maps containing maps

src/ds/ds_htable.c

@@ -705,6 +705,7 @@ void ds_htable_put(ds_htable_t *table, zval *key, zval *value)
     // If found, destruct the current value so that we can replace it.
     if (found) {
         zval_ptr_dtor(&bucket->value);
+        ZVAL_UNDEF(&bucket->value);
     }
 
     if (value) {