calling knit_exit() puts knits in a non-functioning state

[dlampart]

Hi,

We think we discovered the following bug. Let's say we have two reports:

knit_exit.Rmd

---
output: md_document
---

```{r}
knitr::knit_exit()
```

hello.Rmd

---
output: md_document
---

```{r}
print("hello")
```

Now running the following code:

knitr::knit("knit_exit.Rmd")
knitr::knit("hello.Rmd")

will generate an empy hello.md file.

If statements are reversed or there's the unload statement in between:

unloadNamespace("knitr")

the hello.md statement is rendered as expected.

sessionInfo()

R version 4.3.3 (2024-02-29)
Platform: aarch64-apple-darwin23.2.0 (64-bit)
Running under: macOS Sonoma 14.6.1

Matrix products: default
BLAS:   /opt/homebrew/Cellar/openblas/0.3.26/lib/libopenblasp-r0.3.26.dylib 
LAPACK: /opt/homebrew/Cellar/r/4.3.3/lib/R/lib/libRlapack.dylib;  LAPACK version 3.11.0

locale:
[1] en_US.UTF-8/en_US.UTF-8/en_US.UTF-8/C/en_US.UTF-8/en_US.UTF-8

time zone: Europe/Zurich
tzcode source: internal

attached base packages:
[1] stats     graphics  grDevices utils     datasets  methods   base     

other attached packages:
[1] knitr_1.48

loaded via a namespace (and not attached):
[1] compiler_4.3.3 tools_4.3.3    xfun_0.47     

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