fix: prevent errors when using secure connections

[tapayne88]

With my version of curl (v8.7.1), if I use a secure jenkins host I get the following error from the job.

This isn't surfaced very well as it the code errors when trying to decode the empty response

nvim-jenkinsfile-linter/lua/jenkinsfile_linter.lua

Line 33 in b6b48b0

local args = vim.fn.json_decode(concatenated_crumbs)

Job reports the error when logged:

[jenkinsfile-linter]   _stderr_results = { "curl: option : blank argument where content is expected" },
...
[jenkinsfile-linter]   args = { "", "--user", "<username>:<token>", "https://<my-secure-jenkins>/crumbIssuer/api/json" },

This looks to be coming from the insecure parameter which defaults to an empty string when not set via the environment.

This PR should fix this scenario and report job failures more consistently

[tapayne88]

Looks like Job's on_stderr can surface errors from the coroutine as the first argument
https://github.com/nvim-lua/plenary.nvim/blob/2d9b06177a975543726ce5c73fca176cedbffe9d/lua/plenary/job.lua#L333

[tapayne88]

The job will report a summary of errors
https://github.com/nvim-lua/plenary.nvim/blob/2d9b06177a975543726ce5c73fca176cedbffe9d/lua/plenary/job.lua#L616-L622

[sampathpagolu]

I am seeing the same error on MacOS Sequoia, curl 8.9.1. Made some local changes to get it to work. Hoping to see this get merged.

[ckipp01]

I don't use Jenkins anymore, so it's quite hard to test this. This looks good, so I'll just go ahead and say LGTM. Thanks!