Fixed path being unshifted before returned generator exhausted.

I've experienced some request issues on long generator routes, mainly related to SCRIPT_NAME and PATH_INFO changing between yields.
After some debugging I've realized path_shift was being called before yielding, breaking all get_url calls on my partial templates from my mounted app.
This patch fixes that chaining the path_shift to response body, instead of calling right after return.

Remove this, and add `return; yield` at the end of the function to create an empty generator