Add method that check if build has tags

app/models/ci/build.rb

@@ -290,13 +290,15 @@ module Ci
     end
     def can_be_served?(runner)
-      if tag_list.empty? && !runner.run_untagged?
-        return false
-      end
+      return false unless has_tags? || runner.run_untagged?
       (tag_list - runner.tag_list).empty?
     end
+    def has_tags?
+      tag_list.any?
+    end
+
     def any_runners_online?
       project.any_runners? { |runner| runner.active? && runner.online? && can_be_served?(runner) }
     end

spec/models/build_spec.rb

@@ -309,6 +309,18 @@ describe Ci::Build, models: true do
     end
   end
+  describe '#has_tags?' do
+    context 'when build has tags' do
+      subject { create(:ci_build, tag_list: ['tag']) }
+      it { is_expected.to have_tags }
+    end
+
+    context 'when build does not have tags' do
+      subject { create(:ci_build, tag_list: []) }
+      it { is_expected.to_not have_tags }
+    end
+  end
+
   describe '#any_runners_online?' do
     subject { build.any_runners_online? }