Set generate_url to an empty function if none is provided. This will allow us to call this function without checking for None. It is called frequently in generated code

Change-Id: I3b7eb6de6224d8ef7c85aad5c3712a1208360f9c
Merge "Set generate_url to an empty function if none is provided. This will allow us to call this function without checking for None. It is called frequently in generated code"