Got Error While Logging with GitHub

When I try to login with GitHub,an error occurred.
Here is what I got on the error page

Error

...e/luarocks/.luarocks/share/lua/5.1/lapis/application.lua:402: ./applications/github.lua:83: attempt to index local 'user' (a nil value)
stack traceback:
	./applications/github.lua: in function <./applications/github.lua:32>

Traceback

stack traceback:
	[C]: in function 'error'
	...e/luarocks/.luarocks/share/lua/5.1/lapis/application.lua:402: in function 'handler'
	...e/luarocks/.luarocks/share/lua/5.1/lapis/application.lua:131: in function 'resolve'
	...e/luarocks/.luarocks/share/lua/5.1/lapis/application.lua:168: in function <...e/luarocks/.luarocks/share/lua/5.1/lapis/application.lua:166>
	[C]: in function 'xpcall'
	...e/luarocks/.luarocks/share/lua/5.1/lapis/application.lua:174: in function 'dispatch'
	/home/luarocks/.luarocks/share/lua/5.1/lapis/nginx.lua:231: in function 'serve'
	content_by_lua(nginx.conf.compiled:48):1: in main chunk

Another piece of information is that I have registered with the same email address as the one my GitHub account uses

Start in applications/github.lua, especially the handler around line 32 and the failing access at line 83. Reproduce the GitHub login flow and inspect why the user value is nil, including the same-email case described in the report. Done means GitHub login no longer produces this error page.