fix empty chunk on eof

[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:
• system_test:
• zboxcli:
• zwalletcli:
• Other: ...

[codecov-commenter]

Codecov Report

Attention: Patch coverage is 18.18182% with 18 lines in your changes are missing coverage. Please review.

Project coverage is 14.92%. Comparing base (8329e36) to head (a72c4f0). Report is 81 commits behind head on sprint-1.14.

Files	Patch %	Lines
...ode/go/0chain.net/blobbercore/filestore/storage.go	10.00%	8 Missing and 1 partial :warning:
...ain.net/blobbercore/handler/file_command_update.go	0.00%	6 Missing :warning:
...ain.net/blobbercore/handler/file_command_upload.go	50.00%	1 Missing and 2 partials :warning:

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Additional details and impacted files

@@               Coverage Diff               @@
##           sprint-1.14    #1417      +/-   ##
===============================================
- Coverage        15.02%   14.92%   -0.11%     
===============================================
  Files              178      179       +1     
  Lines            19922    20183     +261     
===============================================
+ Hits              2994     3013      +19     
- Misses           16556    16795     +239     
- Partials           372      375       +3     

Flag	Coverage Δ
Unit-Tests	14.92% <18.18%> (-0.11%)	:arrow_down:

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