Update syntax and CHANGELOG for #905 [ci skip]

CHANGELOG.md

@@ -15,7 +15,8 @@ recommendations of [keepachangelog.com](http://keepachangelog.com/).
 
 ### Fixed
 
-- None
+- [#905](https://github.com/airblade/paper_trail/pull/905) - Only invoke
+  `logger.warn` if `logger` instance exists
 
 ## 6.0.1 (2016-12-04)
 

lib/paper_trail/record_trail.rb

@@ -502,10 +502,10 @@ module PaperTrail
     end
 
     def log_version_errors(version, action)
-      version.logger.warn(
+      version.logger && version.logger.warn(
         "Unable to create version for #{action} of #{@record.class.name}" +
           "##{@record.id}: " + version.errors.full_messages.join(", ")
-      ) if version.logger
+      )
     end
 
     # Returns true if the given HABTM association should be saved.