Fix error when CI job variables not specified

lib/ci/gitlab_ci_yaml_processor.rb

@@ -54,7 +54,7 @@ module Ci
       job = @jobs[name.to_sym]
       return [] unless job
 
-      job.fetch(:variables, [])
+      job[:variables] || []
     end
 
     private

spec/lib/ci/gitlab_ci_yaml_processor_spec.rb

@@ -465,6 +465,7 @@ module Ci
         end
 
         context 'when syntax is incorrect' do
+          context 'when variables defined but invalid' do
             it 'raises error' do
               variables = [:KEY1, 'value1', :KEY2, 'value2']
 
@@ -480,6 +481,27 @@ module Ci
                                  /job: variables should be a map/)
             end
           end
+
+          context 'when variables key defined but value not specified' do
+            it 'returns empty array' do
+              config =  YAML.dump(
+                { before_script: ['pwd'],
+                  rspec: {
+                    variables: nil,
+                    script: 'rspec' }
+                })
+
+              config_processor = GitlabCiYamlProcessor.new(config, path)
+
+              ##
+              #  TODO, in next version of CI configuration processor this
+              # should be invalid configuration, see #18775 and #15060
+              #
+              expect(config_processor.job_variables(:rspec))
+                .to be_an_instance_of(Array).and be_empty
+            end
+          end
+        end
       end
 
       context 'when job variables are not defined' do