Fix az-security-requirement for scope with empty value

functions/security-requirements.js

@@ -53,7 +53,7 @@ module.exports = (input, _, context) => {
             });
           }
           scopes.forEach((scope, scopeIndex) => {
-            if (!scheme.scopes[scope]) {
+            if (!(scope in scheme.scopes)) {
               errors.push({
                 message: `Scope "${scope}" is not defined for security scheme "${key}".`,
                 path: [...path, index, key, scopeIndex],

test/security-requirements.test.js

@@ -274,11 +274,22 @@ test('az-security-requirements should find no errors', () => {
         in: 'header',
         description: 'API Key for your subscription',
       },
+      OAuth2Auth: {
+        type: 'oauth2',
+        flow: 'implicit',
+        authorizationUrl: 'https://example.com/oauth2/v2.0/authorize',
+        scopes: {
+          'https://example.com/.default': '',
+        },
+      },
     },
     security: [
       {
         apim_key: [],
       },
+      {
+        OAuth2Auth: ['https://example.com/.default'],
+      },
     ],
   };
   return linter.run(oasDoc).then((results) => {