[actpool] skip adding accounts if pending acts is empty

[Liuhaai]

Description

Please include a summary of the changes and the related issue. Please also include relevant motivation and context. List any dependencies that are required for this change.

Fixes #(issue)

Type of change

Please delete options that are not relevant.

• [] Bug fix (non-breaking change which fixes an issue)
• [] New feature (non-breaking change which adds functionality)
• [] Code refactor or improvement
• [] Breaking change (fix or feature that would cause a new or changed behavior of existing functionality)
• [] This change requires a documentation update

How Has This Been Tested?

Please describe the tests that you ran to verify your changes. Provide instructions so we can reproduce. Please also list any relevant details for your test configuration

• [] make test
• [] fullsync
• [] Other test (please specify)

Test Configuration:

• Firmware version:
• Hardware:
• Toolchain:
• SDK:

Checklist:

• [] My code follows the style guidelines of this project
• [] I have performed a self-review of my code
• [] I have commented my code, particularly in hard-to-understand areas
• [] I have made corresponding changes to the documentation
• [] My changes generate no new warnings
• [] I have added tests that prove my fix is effective or that my feature works
• [] New and existing unit tests pass locally with my changes
• [] Any dependent changes have been merged and published in downstream modules

[sonarcloud]

Quality Gate passed

Kudos, no new issues were introduced!

0 New issues
0 Security Hotspots
No data about Coverage
0.0% Duplication on New Code

See analysis details on SonarCloud

[codecov]

Codecov Report

Attention: 515 lines in your changes are missing coverage. Please review.

Comparison is base (e1f0636) 75.38% compared to head (b5b98c1) 76.30%.
Report is 130 commits behind head on master.

Files	Patch %	Lines
blockindex/contractstaking/event_handler.go	67.23%	45 Missing and 13 partials ⚠️
action/protocol/staking/staking_statereader.go	69.76%	35 Missing and 17 partials ⚠️
action/protocol/execution/evm/evm.go	48.38%	47 Missing and 1 partial ⚠️
action/protocol/staking/protocol.go	33.33%	28 Missing ⚠️
...tion/protocol/staking/contractstake_bucket_type.go	0.00%	24 Missing ⚠️
api/coreservice.go	68.49%	17 Missing and 6 partials ⚠️
blockindex/contractstaking/util.go	39.47%	22 Missing and 1 partial ⚠️
action/protocol/rewarding/fund.go	23.07%	19 Missing and 1 partial ⚠️
api/websocket.go	0.00%	20 Missing ⚠️
blockindex/sgd_indexer.go	90.30%	12 Missing and 7 partials ⚠️
... and 29 more

Additional details and impacted files

@@            Coverage Diff             @@
##           master    #4027      +/-   ##
==========================================
+ Coverage   75.38%   76.30%   +0.92%     
==========================================
  Files         303      330      +27     
  Lines       25923    28264    +2341     
==========================================
+ Hits        19541    21567    +2026     
- Misses       5360     5599     +239     
- Partials     1022     1098      +76     

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