Fix update ExcludeRegex to empty not work

[xiantang]

fix #304

[codecov]

Codecov Report

Merging #308 (1c68182) into master (39482e0) will increase coverage by 2.25%.
The diff coverage is 100.00%.

@@            Coverage Diff             @@
##           master     #308      +/-   ##
==========================================
+ Coverage   66.91%   69.16%   +2.25%     
==========================================
  Files           7        7              
  Lines         943      960      +17     
==========================================
+ Hits          631      664      +33     
+ Misses        246      225      -21     
- Partials       66       71       +5     

Impacted Files	Coverage Δ
runner/config.go	75.11% <100.00%> (+5.11%)	⬆️
runner/engine.go	63.61% <0.00%> (+1.30%)	⬆️
runner/util.go	71.60% <0.00%> (+2.05%)	⬆️

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