A few months ago I submitted a pull request that was merged which adds support for tabularx and xltabular tables for LaTeX in kable. If you use one of these and try to make a table without a caption, you will get an error.

---
output:
  pdf_document:
    extra_dependencies: xltabular
---

```{r, echo = FALSE}
library(knitr)

col1 = c("Lorem", "Ipsum")
col2 = c("Dolor", "Sit")

df = data.frame(col1, col2)

# These two will NOT work
kable(df, "latex", tabular = "tabularx")
kable(df, "latex", tabular = "xltabular")
# These two WILL work
kable(df, "latex", tabular = "tabularx", caption = "")
kable(df, "latex", tabular = "xltabular", caption = "")
```

Here is the error I got:

! Missing number, treated as zero.
<to be read again>
                   l
l.70 \begin{tabularx}{l|l}

Error: LaTeX failed to compile file.tex. See https://yihui.org/tinytex/r/#debugging for debugging tips. See file.log for more info.
Execution halted

shell returned 1

I understand what the problem is, it is using \begin{tabularx}{l|l} instead of \begin{tabularx}{\linewidth}{l|l}. It is strange that not having a caption causes this.

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