Make size optional

[Hitenjain14]

Changes

Fixes

Tests

Tasks to complete before merging PR:

• [ ] Ensure system tests are passing. If not Run them manually to check for any regressions :clipboard:
• [ ] Do any new system tests need added to test this change? do any existing system tests need updated? If so create a PR at 0chain/system_test
• [ ] Merge your system tests PR to master AFTER merging this PR

Associated PRs (Link as appropriate):

• 0chain:
• gosdk: https://github.com/0chain/gosdk/pull/1401
• system_test:
• zboxcli:
• zwalletcli:
• Other: ...

[codecov-commenter]

Codecov Report

Attention: Patch coverage is 48.83721% with 44 lines in your changes are missing coverage. Please review.

Project coverage is 15.02%. Comparing base (c2bd391) to head (786760e).

Files	Patch %	Lines
...ode/go/0chain.net/blobbercore/filestore/storage.go	47.61%	17 Missing and 5 partials :warning:
...et/blobbercore/handler/object_operation_handler.go	47.05%	9 Missing :warning:
...de/go/0chain.net/blobbercore/challenge/protocol.go	0.00%	6 Missing :warning:
...ain.net/blobbercore/handler/file_command_upload.go	0.00%	3 Missing :warning:
...go/0chain.net/blobbercore/allocation/connection.go	0.00%	2 Missing :warning:
...ain.net/blobbercore/handler/file_command_update.go	0.00%	1 Missing :warning:
.../go/0chain.net/blobbercore/reference/objectpath.go	0.00%	1 Missing :warning:

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Additional details and impacted files

```diff @@ Coverage Diff @@ ## sprint-1.13 #1390 +/- ## =============================================== + Coverage 15.01% 15.02% +0.01% =============================================== Files 178 178 Lines 19906 19922 +16 =============================================== + Hits 2989 2994 +5 - Misses 16546 16556 +10 - Partials 371 372 +1 ``` | [Flag](https://app.codecov.io/gh/0chain/blobber/pull/1390/flags?src=pr&el=flags&utm_medium=referral&utm_source=github&utm_content=comment&utm_campaign=pr+comments&utm_term=0chain) | Coverage Δ | | |---|---|---| | [Unit-Tests](https://app.codecov.io/gh/0chain/blobber/pull/1390/flags?src=pr&el=flag&utm_medium=referral&utm_source=github&utm_content=comment&utm_campaign=pr+comments&utm_term=0chain) | `15.02% <48.83%> (+0.01%)` | :arrow_up: | Flags with carried forward coverage won't be shown. [Click here](https://docs.codecov.io/docs/carryforward-flags?utm_medium=referral&utm_source=github&utm_content=comment&utm_campaign=pr+comments&utm_term=0chain#carryforward-flags-in-the-pull-request-comment) to find out more.

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