fix potential refleak in std::array type caster

Author: wjakob

include/nanobind/stl/detail/nb_array.h

@@ -33,10 +33,10 @@ template <typename Array, typename Entry, size_t Size> struct array_caster {
 
  value[i] = caster.operator cast_t<Entry>();
  }
-
- Py_XDECREF(temp);
  }
 
+ Py_XDECREF(temp);
+
  return success;
  }