Give informative error message in boot_networklevel when lst is not a list

[valentinitnelav]

Below, the error message is not that informative:

library(bootstrapnet)
library(bipartite)
data(Safariland)

nest <- Safariland %>% 
  web_matrix_to_df() %>%
  boot_networklevel(col_lower = "lower", # column name for plants
                    col_higher = "higher", # column name for insects
                    index = "nestedness",
                    level = "both", # here, nestedness is not affected by level
                    start = 100,
                    step = 50,
                    n_boot = 30,
                    n_cpu = 3)

Gives

Error in function_list[[k]](value) : 
  `data` must be a data.frame or data.table.  Maybe check out the function web_matrix_to_df() for examples.

Should actually inform that the user didn't provide a list object (in this case it can be a list of one element containing the needed data).