示例中 isEmpty 导致规则不能删除

[foreveryang321]

Describe what this PR does / why we need it
Translated from Google:
In the example isEmpty causes the rule to not be deleted

Does this pull request fix one issue?
NONE

Describe how you did it
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Special notes for reviews

[codecov-io]

Codecov Report

Merging #353 into master will decrease coverage by 0.04%.
The diff coverage is n/a.

@@             Coverage Diff              @@
##             master     #353      +/-   ##
============================================
- Coverage     38.25%   38.21%   -0.05%     
+ Complexity      937      936       -1     
============================================
  Files           218      218              
  Lines          6966     6966              
  Branches        948      948              
============================================
- Hits           2665     2662       -3     
- Misses         3964     3966       +2     
- Partials        337      338       +1

Impacted Files	Coverage Δ	Complexity Δ
...a/csp/sentinel/slots/statistic/base/LeapArray.java	64.55% <0%> (-3.8%)	23% <0%> (-1%)

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[sczyh30]

LGTM

[sczyh30]

Thanks for contributing!