Why "Uncaught ReferenceError: action is not defined" occurs?

While loading rm_release.do form, observed below java script error on browser console,

Uncaught ReferenceError: action is not defined

Below screenshot of error shows the complete stack of exception,

Any supported release. 

Above described error occurs due to the reason that "Client" checkbox is ticked on an UI action, however "Onclick" function and client side code is not written on the UI Action script as shown in the below screenshot,

Since there is no client side code defined, the server-side code is loaded on the on-load of the form and hence server side code breaks as the server side objects will not be available at client side.

Review the UI action, if "Client" checkbox is accidentally ticked, uncheck it.

OR

If client side code execution is needed, define onClick method and write client side code in script section, so that server-side code is only executed at server side upon client side code is successfully completed. 

UI Actions

Create a UI Action