return empty arrays instead of nil in ci_config

Author: ianfixes

CHANGELOG.md

@@ -17,6 +17,7 @@ and this project adheres to [Semantic Versioning](http://semver.org/).
 
 ### Fixed
 - Replaced pipes with `Open3.capture3` to avoid deadlocks when commands have too much output
+- `ci_config.rb` now returns empty arrays (instead of nil) for undefined config keys
 
 ### Security
 

lib/arduino_ci/ci_config.rb

@@ -200,12 +200,14 @@ def package_url(package)
     # platforms to build [the examples on]
     # @return [Array<String>] The platforms to build
     def platforms_to_build
+      return [] if @compile_info[:platforms].nil?
       @compile_info[:platforms]
     end
 
     # platforms to unit test [the tests on]
     # @return [Array<String>] The platforms to unit test on
     def platforms_to_unittest
+      return [] if @unittest_info[:platforms].nil?
       @unittest_info[:platforms]
     end