Error in stop_vctrs() ! Input must be a vector, not an environment.

[wenyuhaokikika]

Describe the bug
I run the script

TeX('$\\alpha^\\beta$')

and it raise Exception:

Error in `stop_vctrs()`:
! Input must be a vector, not an environment.
Traceback:

TeX("$\\alpha^\\beta$")
parse_latex(input)
validate_input(latex_string)
str_detect(latex_string, fixed(possible_slash_pattern))
check_lengths(string, pattern)
vctrs::vec_size_common(string = string, pattern = pattern, replacement = replacement, 
 .     .call = error_call)
stop_scalar_type(.Primitive("quote")(<environment>), "")
stop_vctrs(msg, "vctrs_error_scalar_type", actual = x)
abort(message, class = c(class, "vctrs_error"), ...)
signal_abort(cnd, .file)

To Reproduce

1. Paste the output of sessionInfo() (this should show, at minimum, the version of R, the platform, and the architecture you are running on)

R version 3.5.0 (2018-04-23)
Platform: x86_64-pc-linux-gnu (64-bit)
Running under: CentOS Linux 7 (Core)

Matrix products: default
BLAS: /home/wyh/anaconda3/lib/R/lib/libRblas.so
LAPACK: /home/wyh/anaconda3/lib/R/lib/libRlapack.so

locale:
 [1] LC_CTYPE=en_US.UTF-8       LC_NUMERIC=C              
 [3] LC_TIME=en_US.UTF-8        LC_COLLATE=en_US.UTF-8    
 [5] LC_MONETARY=en_US.UTF-8    LC_MESSAGES=en_US.UTF-8   
 [7] LC_PAPER=en_US.UTF-8       LC_NAME=C                 
 [9] LC_ADDRESS=C               LC_TELEPHONE=C            
[11] LC_MEASUREMENT=en_US.UTF-8 LC_IDENTIFICATION=C       

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

other attached packages:
[1] latex2exp_0.9.6

loaded via a namespace (and not attached):
 [1] fansi_0.5.0     utf8_1.2.2      digest_0.6.15   crayon_1.3.4   
 [5] IRdisplay_0.5.0 repr_0.15.0     lifecycle_1.0.3 jsonlite_1.5   
 [9] magrittr_2.0.1  evaluate_0.15   pillar_1.6.4    stringi_1.7.12 
[13] rlang_1.1.1     cli_3.6.1       uuid_0.1-2      ellipsis_0.3.2 
[17] vctrs_0.3.8     IRkernel_1.1.1  tools_3.5.0     stringr_1.5.0  
[21] glue_1.6.2      fastmap_1.1.0   compiler_3.5.0  base64enc_0.1-3
[25] htmltools_0.5.2 pbdZMQ_0.3-3   

2. Include a short snippet of code I can use to reproduce the problem. You can use reprex::reprex() to quickly prepare a reproducible example.

3. What environment are plotting from? (e.g. RStudio, the R Console, Visual Studio Code, etc.)
   I use jupyter jupyter_server : 1.24.0, anaconda ,centos7.

4. If the bug comprises unexpected visual output from TeX(), please paste a screenshot of what you see on your system. You can plot a single TeX expression by running

# example
library(latex2exp)
plot(TeX(r"($\alpha + \beta$)")) # <-- this doesn't render correctly

It raise Exception

Error in parse(text = x, srcfile = src): <text>:3:11: unexpected string constant
library(latex2exp)
plot(TeX(r"($\alpha + \beta$)"
             ^
Traceback: