I am unable to upload a pdf file

The follow message is displayed when I try to upload a pdf file:

• Request error: The URL returned a 404 (not found): /umbraco/backoffice/UmbracoApi/Media/PostSave with data: {"key":"contentItem","value":{"id":0,"properties":[{"id":0,"alias":"umbracoExtension","value":""},{"id":0,"alias":"umbracoFile","value":{"selectedFiles":"Umbraco-7-Editors-Manual.pdf"}},{"id":0,"alias":"umbracoBytes","value":""}],"name":"Test File","contentTypeAlias":"File","parentId":3567,"action":"saveNew"}} Contact your administrator for information.

In the browser console I see the following error:

• POST http://localhost:50719/umbraco/backoffice/UmbracoApi/Media/PostSave 404 (Not Found)
• TypeError: Cannot read property 'length' of undefined at Object.getAllProps (umbraco.services.js?cdv=595780144:962) at Object.reBindChangedProperties (umbraco.services.js?cdv=595780144:1091) at umbraco.controllers.js?cdv=595780144:6857 at o (angular.min.js?cdv=595780144:80) at angular.min.js?cdv=595780144:81 at Object.e.$eval (angular.min.js?cdv=595780144:92) at Object.e.$digest (angular.min.js?cdv=595780144:90) at Object.e.$apply (angular.min.js?cdv=595780144:92) at j (angular.min.js?cdv=595780144:101) at r (angular.min.js?cdv=595780144:104)

I started getting the error after I upgraded to version 7.4