Survive on job exceptions during candidate gathering

[KostyaSha]

Fixes #211

This change is 

[codecov-io]

Codecov Report

Merging #217 into master will increase coverage by 0.95%.
The diff coverage is 96.87%.

@@             Coverage Diff             @@
##             master    #217      +/-   ##
===========================================
+ Coverage     54.45%   55.4%   +0.95%     
- Complexity      603     610       +7     
===========================================
  Files           113     113              
  Lines          2966    2976      +10     
  Branches        243     243              
===========================================
+ Hits           1615    1649      +34     
+ Misses         1261    1239      -22     
+ Partials         90      88       -2

Impacted Files	Coverage Δ	Complexity Δ
...hub/pullrequest/webhook/WebhookInfoPredicates.java	91.3% <100%> (+2.41%)	3 <0> (ø)	⬇️
...b/pullrequest/webhook/GHPullRequestSubscriber.java	78.37% <100%> (ø)	9 <1> (+1)	⬆️
...on/branch/webhook/WebhookInfoBranchPredicates.java	91.3% <100%> (+57.97%)	3 <0> (+2)	⬆️
...integration/branch/webhook/GHBranchSubscriber.java	32.55% <87.5%> (+27.9%)	5 <1> (+4)	⬆️
...ci/plugins/github/pullrequest/GitHubPRTrigger.java	67.24% <0%> (+0.86%)	18% <0%> (ø)	⬇️
...github/integration/branch/GitHubBranchTrigger.java	62.72% <0%> (+0.9%)	17% <0%> (ø)	⬇️

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