Fixes issues with TypeError:Passed nil into T.must (#10603)

* Fixes unescaped error handler

npm_and_yarn/lib/dependabot/npm_and_yarn/registry_parser.rb

@@ -45,7 +45,8 @@ def dependency_name
                      resolved_url
                    end
 
-        T.must(T.must(url_base[/@.*/]).gsub("%2F", "/").split("/")[0..1]).join("/")
+        package_name = url_base.gsub("%2F", "/").match(%r{@.*/})
+        "#{T.must(package_name)}#{T.must(url_base.gsub('%2F', '/').split('/').last)}"
       end
 
       private

npm_and_yarn/spec/dependabot/npm_and_yarn/file_updater/pnpm_lockfile_updater_spec.rb

@@ -93,6 +93,15 @@
       end
     end
 
+    context "when there is a lockfile with tarball urls we don't have access to" do
+      let(:project_name) { "pnpm/private_package_access" }
+
+      it "raises a helpful error" do
+        expect { updated_pnpm_lock_content }
+          .to raise_error(Dependabot::PrivateSourceAuthenticationFailure)
+      end
+    end
+
     context "when there is a unsupported engine response from registry" do
       let(:dependency_name) { "@blocknote/core" }
       let(:version) { "0.15.4" }

npm_and_yarn/spec/fixtures/projects/pnpm/private_package_access/.npmrc

@@ -0,0 +1 @@
+@private-pkg:registry=https://npm.pkg.github.com

npm_and_yarn/spec/fixtures/projects/pnpm/private_package_access/package.json

@@ -0,0 +1,5 @@
+{
+  "dependencies": {
+    "@private-pkg/inner-source-top-secret-npm-2": "1.0.3"
+  }
+}