fix: preserve default values in x-goog-request-params header (#26)

- [ ] Regenerate this pull request now.

PiperOrigin-RevId: 474338479

Source-Link: googleapis/googleapis@d5d35e0

Source-Link: https://github.com/googleapis/googleapis-gen/commit/efcd3f93962a103f68f003e2a1eecde6fa216a27
Copy-Tag: eyJwIjoiLmdpdGh1Yi8uT3dsQm90LnlhbWwiLCJoIjoiZWZjZDNmOTM5NjJhMTAzZjY4ZjAwM2UyYTFlZWNkZTZmYTIxNmEyNyJ9

src/v2/services_client.ts

@@ -590,7 +590,7 @@ export class ServicesClient {
     options.otherArgs.headers = options.otherArgs.headers || {};
     options.otherArgs.headers['x-goog-request-params'] =
       this._gaxModule.routingHeader.fromParams({
-        resource: request.resource || '',
+        resource: request.resource ?? '',
       });
     this.initialize();
     return this.innerApiCalls.getIamPolicy(request, options, callback);
@@ -686,7 +686,7 @@ export class ServicesClient {
     options.otherArgs.headers = options.otherArgs.headers || {};
     options.otherArgs.headers['x-goog-request-params'] =
       this._gaxModule.routingHeader.fromParams({
-        resource: request.resource || '',
+        resource: request.resource ?? '',
       });
     this.initialize();
     return this.innerApiCalls.setIamPolicy(request, options, callback);
@@ -777,7 +777,7 @@ export class ServicesClient {
     options.otherArgs.headers = options.otherArgs.headers || {};
     options.otherArgs.headers['x-goog-request-params'] =
       this._gaxModule.routingHeader.fromParams({
-        resource: request.resource || '',
+        resource: request.resource ?? '',
       });
     this.initialize();
     return this.innerApiCalls.testIamPermissions(request, options, callback);