message: Fix a warning in 32-bit builds
diff: @@ -532,8 +532,9 @@ void GroupWriter::merge_free_space()
  // Merge
  size_t size2 = to_size_t(m_free_lengths.get(i2));
  - REALM_ASSERT_RELEASE_EX(size1 < (1ULL << 63) && size2 < (1ULL << 63), size1, size2);
  - m_free_lengths.set(i, size1 + size2);
  + size_t new_size = size1 + size2;
  + REALM_ASSERT_RELEASE_EX(new_size > size1 && new_size > size2, size1, size2, new_size);
  + m_free_lengths.set(i, new_size);
  m_free_positions.erase(i2);
  m_free_lengths.erase(i2);
  if (is_shared)
  