correct erroneous deletion

Author: monofonik

test/spec/modules/appnexusBidAdapter_spec.js

@@ -148,6 +148,7 @@ describe('AppNexusAdapter', function () {
     });
 
     it('should not populate the ad_types array when adUnit.mediaTypes is undefined', function() {
+      const bidRequest = Object.assign({}, bidRequests[0]);
       const request = spec.buildRequests(bidRequests);
       const payload = JSON.parse(request.data);