rewrite_by_lua_block {;} in nginx-kong.conf file causes run-time syntax issues

[p-thamke]

With kong 3.9.1, when we hit our service api, kong crashes and throws 500 internal server error with following logs:

2025/11/25 13:30:22 [error] 10601#0: 1289 failed to run balancer_by_lua: .../luarocks/share/lua/5.1/kong/init.lua:1432: attempt to call upvalue 'enable_keepalive' (a nil value)
stack traceback:
.../luarocks/share/lua/5.1/kong/init.lua:1432: in function 'balancer'
balancer_by_lua(nginx-kong.conf:72):2: in main chunk while connecting to upstream, client: 172.17.0.32, server: kong, request: "GET /v1/api HTTP/1.1", host: "url:port", request_id: "******************************"
2025/11/25 13:30:22 [error] 10601#0: *1289 failed to load inlined Lua code: rewrite_by_lua(nginx-kong.conf:330):1: unexpected symbol near ';', client: 172.17.0.32

nginx-kong.conf has following text at line 330 (which looks to be a syntax error from lua point of view):
rewrite_by_lua_block {;}

This error seems to be coming from the kong open source code in file "nginx_kong.lua" line "rewrite_by_lua_block {;}" but we are not sure on this.

Expected Behavior
Expected response is 200 Ok for the service api hit through kong api gateway

Steps To Reproduce
As mentioned in description, we are running kong 3.9.1.
Hit our service api through kong (using curl on command line)
kong crashes and throws 500 internal server error response.
Error logs show the syntax error for rewrite_by_lua_block {;} most likely from file nginx_kong.lua.

Note: We are not adding any additional nginx lua code from any of our modules.

We request inputs for this run time error. We've raised an issue as well for this - #14796

Thanks.