FastCGI sent in stderr: "Primary script unknown" flooding error log of a site

```bash
root@vultr:~# ee cli info
+-------------------+----------------------------------------------------------------------------+
| OS | Linux 4.15.0-42-generic #45-Ubuntu SMP Thu Nov 15 19:32:57 UTC 2018 x86_64 |
| Shell | /bin/bash |
| PHP binary | /usr/bin/php7.2 |
| PHP version | 7.2.13-1+ubuntu18.04.1+deb.sury.org+1 |
| php.ini used | /etc/php/7.2/cli/php.ini |
| EE root dir | phar://ee.phar |
| EE vendor dir | phar://ee.phar/vendor |
| EE phar path | /root |
| EE packages dir | |
| EE global config | /opt/easyengine/config/config.yml |
| EE project config | |
| EE version | 4.0.5 |
+-------------------+----------------------------------------------------------------------------+

root@vultr:~# lsb_release -a
No LSB modules are available.
Distributor ID: Ubuntu
Description: Ubuntu 18.04.1 LTS
Release: 18.04
Codename: bionic

root@vultr:~# docker version
Client:
Version: 18.09.0
API version: 1.39
Go version: go1.10.4
Git commit: 4d60db4
Built: Wed Nov 7 00:49:01 2018
OS/Arch: linux/amd64
Experimental: false

Server: Docker Engine - Community
Engine:
Version: 18.09.0
API version: 1.39 (minimum version 1.12)
Go version: go1.10.4
Git commit: 4d60db4
Built: Wed Nov 7 00:16:44 2018
OS/Arch: linux/amd64
Experimental: false

root@vultr:~# docker-compose version
docker-compose version 1.23.2, build 1110ad01
docker-py version: 3.6.0
CPython version: 3.6.7
OpenSSL version: OpenSSL 1.1.0f 25 May 2017
```
I was looking through the NGINX/PHP error log (thanks to the 4.0.3 update) and am seeing a stream of these errors from a WordPress plugin I use. . .

```bash
2018/12/12 22:59:00 [error] 7#7: *377622 FastCGI sent in stderr: "Primary script unknown" while reading response header from upstream, client: 86.7.18.7, server: www.playstoresales.com, request: "GET /OneSignalSDKWorker.js.php HTTP/1.1", upstream: "fastcgi://172.23.0.3:9000", host: "www.playstoresales.com", referrer: "https://www.playstoresales.com/OneSignalSDKWorker.js.php"
2018/12/12 22:59:04 [error] 7#7: *377660 FastCGI sent in stderr: "Primary script unknown" while reading response header from upstream, client: 171.235.33.82, server: www.playstoresales.com, request: "GET /OneSignalSDKWorker.js.php HTTP/1.1", upstream: "fastcgi://172.23.0.3:9000", host: "www.playstoresales.com", referrer: "https://www.playstoresales.com/OneSignalSDKWorker.js.php"
2018/12/12 22:59:45 [error] 7#7: *377752 FastCGI sent in stderr: "Primary script unknown" while reading response header from upstream, client: 96.48.108.212, server: www.playstoresales.com, request: "GET /OneSignalSDKWorker.js.php HTTP/1.1", upstream: "fastcgi://172.23.0.3:9000", host: "www.playstoresales.com", referrer: "https://www.playstoresales.com/OneSignalSDKWorker.js.php"
2018/12/12 23:00:04 [error] 7#7: *377764 FastCGI sent in stderr: "Primary script unknown" while reading response header from upstream, client: 109.117.76.81, server: www.playstoresales.com, request: "GET /OneSignalSDKWorker.js.php HTTP/1.1", upstream: "fastcgi://172.23.0.3:9000", host: "www.playstoresales.com", referrer: "https://www.playstoresales.com/OneSignalSDKWorker.js.php"
2018/12/12 23:00:16 [error] 7#7: *377785 FastCGI sent in stderr: "Primary script unknown" while reading response header from upstream, client: 180.251.132.183, server: www.playstoresales.com, request: "GET /OneSignalSDKWorker.js.php HTTP/1.1", upstream: "fastcgi://172.23.0.3:9000", host: "www.playstoresales.com", referrer: "https://www.playstoresales.com/OneSignalSDKWorker.js.php"
2018/12/12 23:00:19 [error] 7#7: *377787 FastCGI sent in stderr: "Primary script unknown" while reading response header from upstream, client: 78.230.155.176, server: www.playstoresales.com, request: "GET /OneSignalSDKWorker.js.php HTTP/1.1", upstream: "fastcgi://172.23.0.3:9000", host: "www.playstoresales.com", referrer: "https://www.playstoresales.com/OneSignalSDKWorker.js.php"
2018/12/12 23:00:26 [error] 7#7: *377791 FastCGI sent in stderr: "Primary script unknown" while reading response header from upstream, client: 110.138.124.188, server: www.playstoresales.com, request: "GET /OneSignalSDKWorker.js.php HTTP/1.1", upstream: "fastcgi://172.23.0.3:9000", host: "www.playstoresales.com", referrer: "https://www.playstoresales.com/OneSignalSDKWorker.js.php"
2018/12/12 23:00:40 [error] 7#7: *377793 FastCGI sent in stderr: "Primary script unknown" while reading response header from upstream, client: 173.167.183.149, server: www.playstoresales.com, request: "GET /OneSignalSDKWorker.js.php HTTP/1.1", upstream: "fastcgi://172.23.0.3:9000", host: "www.playstoresales.com", referrer: "https://www.playstoresales.com/OneSignalSDKWorker.js.php"
2018/12/12 23:00:43 [error] 7#7: *377795 FastCGI sent in stderr: "Primary script unknown" while reading response header from upstream, client: 64.88.211.130, server: www.playstoresales.com, request: "GET /OneSignalSDKWorker.js.php HTTP/1.1", upstream: "fastcgi://172.23.0.3:9000", host: "www.playstoresales.com", referrer: "https://www.playstoresales.com/OneSignalSDKWorker.js.php"
2018/12/12 23:00:48 [error] 7#7: *377805 FastCGI sent in stderr: "Primary script unknown" while reading response header from upstream, client: 107.77.207.172, server: www.playstoresales.com, request: "GET /OneSignalSDKWorker.js.php HTTP/1.1", upstream: "fastcgi://172.23.0.3:9000", host: "www.playstoresales.com", referrer: "https://www.playstoresales.com/OneSignalSDKWorker.js.php"
2018/12/12 23:00:57 [error] 7#7: *377816 FastCGI sent in stderr: "Primary script unknown" while reading response header from upstream, client: 116.37.111.175, server: www.playstoresales.com, request: "GET /OneSignalSDKWorker.js.php HTTP/1.1", upstream: "fastcgi://172.23.0.3:9000", host: "www.playstoresales.com", referrer: "https://www.playstoresales.com/OneSignalSDKWorker.js.php"
2018/12/12 23:01:18 [error] 7#7: *377844 FastCGI sent in stderr: "Primary script unknown" while reading response header from upstream, client: 27.246.32.148, server: www.playstoresales.com, request: "GET /OneSignalSDKWorker.js.php HTTP/1.1", upstream: "fastcgi://172.23.0.3:9000", host: "www.playstoresales.com", referrer: "https://www.playstoresales.com/OneSignalSDKWorker.js.php"
2018/12/12 23:01:45 [error] 7#7: *377859 FastCGI sent in stderr: "Primary script unknown" while reading response header from upstream, client: 89.204.137.126, server: www.playstoresales.com, request: "GET /OneSignalSDKWorker.js.php HTTP/1.1", upstream: "fastcgi://172.23.0.3:9000", host: "www.playstoresales.com", referrer: "https://www.playstoresales.com/OneSignalSDKWorker.js.php"
2018/12/12 23:01:57 [error] 7#7: *377882 FastCGI sent in stderr: "Primary script unknown" while reading response header from upstream, client: 39.125.30.180, server: www.playstoresales.com, request: "GET /OneSignalSDKWorker.js.php HTTP/1.1", upstream: "fastcgi://172.23.0.3:9000", host: "www.playstoresales.com", referrer: "https://www.playstoresales.com/OneSignalSDKWorker.js.php"`
```

Doing a search on "FastCGI sent in stderr: "Primary script unknown" while reading response header from upstream" led me to this page

- https://serverfault.com/questions/517190/nginx-1-fastcgi-sent-in-stderr-primary-script-unknown

With the top answer saying. . .

> The error message “primary script unknown” is almost always related to a wrongly set SCRIPT_FILENAME in the nginx fastcgi_param directive (or incorrect permissions

I was just curious if there was some kind of conflict with EE4 and the OneSignal plugin that I use, or is there something configured incorrectly with NGINX within EE4?