hts cannot create a hierarchical time series for a single observation about hts HOT 1 CLOSED

library(hts)
#> Loading required package: forecast
#> Registered S3 method overwritten by 'quantmod':
#>   method            from
#>   as.zoo.data.frame zoo

nodes <- list(2, c(3, 2))
abc <- ts(5 + matrix(sort(rnorm(500)), ncol = 5, nrow = 100))
hts(abc[1, , drop = FALSE], nodes)
#> Since argument characters are not specified, the default labelling system is used.
#> Hierarchical Time Series 
#> 3 Levels 
#> Number of nodes at each level: 1 2 5 
#> Total number of series: 8 
#> Number of observations per series: 1 
#> Top level series: 
#> Time Series:
#> Start = 1 
#> End = 1 
#> Frequency = 1 
#> [1] 22.10018