Error [!Misplaced \noalign] for PDF output when using row_group_label_position ='stack'

[hgong1]

Describe the bug
Creating PDF output using collapse_rows & row_group_label_position ='stack' will generate [!Misplaced \noalign] errors in some cases. No error will be shown if not using "stack" for row_group_label_position. I am using kableExtra version 1.3.4. Here is the error message:

! Misplaced \noalign.
\addlinespace ->\noalign 
                         {\ifnum 0=`}\fi \@ifnextchar [{\@addspace }{\@addsp...
l.92 \hspace{1em}\addlinespace
                              [0.3em] 

To Reproduce
The following code will generate the error:

data <- data.frame (
  rowGroup = c("row_group1", "row_group1", "row_group1", "row_group2", "row_group2"),
  rowName = c(1, 2, 3, 1, 2),
  A = c("1.83", "58.23", "0.29", "1.83", "57.62"),
  B = c("3.00", "1.00", "3.00", "3.00", "1.00"),
  C = c("80.00", "80.00", "80.00", "80.00", "80.00")
)
kbl(data, booktabs = T, align = "c") %>% 
  collapse_rows(1:2, latex_hline = 'custom', custom_latex_hline = 1:2, row_group_label_position = 'stack')

I have looked into the generated .tex file. The following content has been put in the wrong location in the file:

\hspace{1em}\addlinespace[0.3em]
\multicolumn{5}{l}{\textbf{\textbf{row\_group2}}}\\

The error will not appear if I change the first data point in C from "80.00" to any other number. For example: C = c("80.01", "80.00", "80.00", "80.00", "80.00").