Fix eula_url in product serializer

app/serializers/v3/product_serializer.rb

@@ -25,7 +25,7 @@ def arch
   end
 
   def eula_url
-    if object.eula_url
+    if object.eula_url.present?
       RMT::Misc.replace_uri_parts(object.eula_url, base_url + RMT::DEFAULT_MIRROR_URL_PREFIX)
     else
       ''

spec/serializers/v3/product_serializer_spec.rb

@@ -11,6 +11,26 @@
   end
   let(:base_url) { 'http://example.com' }
 
+  describe 'eula_url' do
+    it 'handles empty string' do
+      product = create(:product, eula_url: '')
+      serializer = described_class.new(product, root_product: sles15, base_url: base_url)
+      expect(serializer.eula_url).to eq('')
+    end
+
+    it 'handles nil string' do
+      product = create(:product, eula_url: nil)
+      serializer = described_class.new(product, root_product: sles15, base_url: base_url)
+      expect(serializer.eula_url).to eq('')
+    end
+
+    it 'handles url' do
+      product = create(:product, eula_url: 'http://example.com/eula')
+      serializer = described_class.new(product, root_product: sles15, base_url: base_url)
+      expect(serializer.eula_url).to eq('http://example.com/repo/eula')
+    end
+  end
+
   describe 'SLES extension tree' do
     subject(:serializer) { described_class.new(sles15, root_product: sles15, base_url: base_url) }