[Test Failure] XML parse standard xml spec fails intermittently

[robbavey]

https://app.travis-ci.com/github/logstash-plugins/logstash-filter-xml/jobs/572873011

logstash_1_6865b4f90b69 | Failures:
logstash_1_6865b4f90b69 | 
logstash_1_6865b4f90b69 |   1) LogStash::Filters::Xml parse standard xml (Deprecated checks) "{\"raw\":\"<foo><key1><key2>value</key2></key1></foo>\"..." processes events as specified
logstash_1_6865b4f90b69 |      Failure/Error: insist { subject.get("tags") }.nil?
logstash_1_6865b4f90b69 |      
logstash_1_6865b4f90b69 |      NoMethodError:
logstash_1_6865b4f90b69 |        undefined method `get' for nil:NilClass
logstash_1_6865b4f90b69 |        Did you mean?  getc
logstash_1_6865b4f90b69 |                       gets
logstash_1_6865b4f90b69 |                       gem
logstash_1_6865b4f90b69 |      # ./spec/filters/xml_spec.rb:31:in `block in <main>'
logstash_1_6865b4f90b69 |      # ./spec/filters/xml_spec.rb:31:in `block in <main>'
logstash_1_6865b4f90b69 | 
logstash_1_6865b4f90b69 | Finished in 18.82 seconds (files took 9.78 seconds to load)
logstash_1_6865b4f90b69 | 40 examples, 1 failure
logstash_1_6865b4f90b69 | 
logstash_1_6865b4f90b69 | Failed examples:
logstash_1_6865b4f90b69 | 
logstash_1_6865b4f90b69 | rspec ./spec/filters/xml_spec.rb:30 # LogStash::Filters::Xml parse standard xml (Deprecated checks) "{\"raw\":\"<foo><key1><key2>value</key2></key1></foo>\"..." processes events as specified
logstash_1_6865b4f90b69 | 
logstash_1_6865b4f90b69 | Randomized with seed 59710