refactor: code optimisation

[piglig]

1. [env/server/server.go] strings.Contains instead of strings.Index
2. [extension/file_test.go] type assertion to the same type
3. [storage/event_dispatch.go] simplifying error checking
4. [storage/repository.go] when checking the length of map[string]interface{}, the nil check can be ignored
5. code comment formatting

[mergify[bot]]

感谢您提出Pull Request，我会尽快Review。我会在1-2日内进行查看或者回复，如果遇到节假日可能会处理较慢，敬请谅解。

[coveralls]

Pull Request Test Coverage Report for Build 5428784400

Warning: This coverage report may be inaccurate.

This pull request's base commit is no longer the HEAD commit of its target branch. This means it includes changes from outside the original pull request, including, potentially, unrelated coverage changes.

• For more information on this, see Tracking coverage changes with pull request builds.
• To avoid this issue with future PRs, see these Recommended CI Configurations.
• For a quick fix, rebase this PR at GitHub. Your next report should be accurate.

Details

• 12 of 18 (66.67%) changed or added relevant lines in 3 files are covered.
• 2 unchanged lines in 1 file lost coverage.
• Overall coverage increased (+0.07%) to 74.078%

---

Changes Missing Coverage	Covered Lines	Changed/Added Lines	%
env/server/server.go	0	1	0.0%
storage/repository.go	11	16	68.75%
<!--	Total:	12	18	66.67%	-->

Files with Coverage Reduction	New Missed Lines	%
storage/repository.go	2	76.59%
<!--	Total:	2		-->

Totals
Change from base Build 4328954728:	0.07%
Covered Lines:	1286
Relevant Lines:	1736

---

💛 - Coveralls