[BlobStorage] Fixing potential overflow

Bug: 779314
Change-Id: I74612639d20544e4c12230569c7b88fbe669ec03
Reviewed-on: https://chromium-review.googlesource.com/747725
Reviewed-by: Victor Costan <pwnall@chromium.org>
Commit-Queue: Daniel Murphy <dmurph@chromium.org>
Cr-Commit-Position: refs/heads/master@{#512977}
std::unique_ptr<BlobDataHandle> BlobStorageContext::GetBlobDataFromUUID(
    const std::string& uuid) {
  BlobEntry* entry = registry_.GetEntry(uuid);
  if (!entry)
    return nullptr;
  return CreateHandle(uuid, entry);
}

std::unique_ptr<BlobDataHandle> BlobStorageContext::GetBlobDataFromUUID(
    const std::string& uuid) {
  BlobEntry* entry = registry_.GetEntry(uuid);
  if (!entry)
    return nullptr;
  return CreateHandle(uuid, entry);
}
