Treat "" as nil for external commit status description

lib/gitlab/ci/status/external/common.rb

@@ -6,7 +6,7 @@ module Gitlab
       module External
         module Common
           def label
-            subject.description || super
+            subject.description.presence || super
           end
 
           def has_details?

spec/lib/gitlab/ci/status/external/common_spec.rb

@@ -21,13 +21,21 @@ describe Gitlab::Ci::Status::External::Common do
       expect(subject.label).to eq external_description
     end
 
-    context 'when description is not set' do
+    context 'when description is nil' do
       let(:external_description) { nil }
 
       it 'uses core status label' do
         expect(subject.label).to eq('passed')
       end
     end
+
+    context 'when description is empty string' do
+      let(:external_description) { '' }
+
+      it 'uses core status label' do
+        expect(subject.label).to eq('passed')
+      end
+    end
   end
 
   describe '#has_action?' do