Fix trivial pmd warnings

[XiongKezhi]

We missed some warnings when adding FlowExecutionAnalyzer, it's better to fix them.

[codecov]

Codecov Report

Merging #86 (b20c9f5) into master (2933c6b) will decrease coverage by 0.09%.
The diff coverage is 55.55%.

@@             Coverage Diff              @@
##             master      #86      +/-   ##
============================================
- Coverage     87.21%   87.11%   -0.10%     
  Complexity      142      142              
============================================
  Files            16       16              
  Lines           649      652       +3     
  Branches         49       49              
============================================
+ Hits            566      568       +2     
- Misses           65       66       +1     
  Partials         18       18              

Impacted Files	Coverage Δ	Complexity Δ
.../checks/status/AbstractStatusChecksProperties.java	50.00% <ø> (ø)	1.00 <0.00> (ø)
...s/plugins/checks/status/FlowExecutionAnalyzer.java	80.41% <55.55%> (-0.30%)	44.00 <2.00> (ø)

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[mrginglymus]

Oops, sorry! I’m too used to zero tolerance static analysis...