[solved]: error "Result 1 must be a single string, not NULL of length 0"

[mariegosme]

It happens often to get the uninformative error "Result 1 must be a single string, not NULL of length 0" (e.g. in issue #129 for build_hisafe, it happened also in define_hisafe and in read_hisafe when using user-defined templates with files that were modified "by hand"). This error is thrown by the function read_param_file when reading a user-modified file (.plt, .tree, .tec, .sim...) that contains "mistakes". Frequent mistakes are:

• line which contains characters that are invisible for the user (such as tabs): hisafer tries to read them and cannot split the line by = to find the parameter name and value. Solution: delete the invisible characters
• commented lines that contain two # but are not supposed to be block titles. Solution keep exactly the same format as example files: ## indicates a block title (e.g. ## TREE PRUNING) do not modify these titles, even changing from uppercase to lowercase will break the code ; # indicates that the line is commented out for hi-sAFe (but hisafer needs to see it anyway)

[mariegosme]

A solution for the first case (line containing characters that cannot be interpreted as either a block title, nor a parameter value) could be to check that line.text contains "=" before line 87 in params.R (element.vals <- purrr::map_chr(strsplit(line.text, split = "=", fixed = TRUE), 2) )