message: Update alloc_slab.cpp
diff: @@ -616,7 +616,7 @@ void SlabAlloc::do_free(ref_type ref, char* addr) noexcept
  prev--;
  REALM_ASSERT_RELEASE_EX(prev->first + prev->second <= ref, ref, size, prev->first, prev->second);
  - // See if element can be combined with next element
  + // See if element can be combined with previous element
  // We can do that just by adding the size
  if (prev->first + prev->second == ref) {
  prev->second += size;
  @@ -641,7 +641,7 @@ void SlabAlloc::do_free(ref_type ref, char* addr) noexcept
  size = (size + 7) & ~0x7;
  FreeBlock* e = reinterpret_cast<FreeBlock*>(addr);
  - REALM_ASSERT(size < 2UL * 1024 * 1024 * 1024);
  + REALM_ASSERT_RELEASE(size < 2UL * 1024 * 1024 * 1024);
  mark_freed(e, static_cast<int>(size));
  free_block(ref, e);
  }
  