Fix ArgumentError Malformed version number in github actions

github_actions/lib/dependabot/github_actions/update_checker.rb

@@ -76,7 +76,8 @@ def updated_requirements
       sig { returns(T::Array[Dependabot::SecurityAdvisory]) }
       def active_advisories
         security_advisories.select do |advisory|
-          advisory.vulnerable?(version_class.new(git_commit_checker.most_specific_tag_equivalent_to_pinned_ref))
+          version = git_commit_checker.most_specific_tag_equivalent_to_pinned_ref
+          version.nil? ? false : advisory.vulnerable?(version_class.new(version))
         end
       end
 

github_actions/spec/dependabot/github_actions/update_checker_spec.rb

@@ -810,7 +810,7 @@
       it { is_expected.to eq(expected_requirements) }
     end
 
-    context "when a vulnerable dependency hase a major tag reference" do
+    context "when a vulnerable dependency has a major tag reference" do
       let(:dependency_name) { "kartverket/github-workflows" }
       let(:reference) { "v2" }
 
@@ -840,6 +840,14 @@
             expect(updated_requirements.first[:source][:ref]).to eq("v3")
           end
         end
+
+        context "when no matching tag with a higher version is available" do
+          let(:upload_pack_fixture) { "github-workflows-no-tags" }
+
+          it "stays on the vulnerable version" do
+            expect(updated_requirements.first[:source][:ref]).to eq(reference)
+          end
+        end
       end
     end