dot-replace_null_fns: Replace NULL functions
In MiguelRodo/gamlsspipeline:

Replaces functions that are NULL or missing in a specified environment with functions whose body is NULL; NULL and have empty arguments as specified.

1	.replace_null_fns(env, expected_params)

`env`	environment. Environment in which the functions are to be found and replaced.
`expected_params`	named list. Names are names of functions in `env` and values are character vectors specifying parameters for functions.

env_curr <- environment()
fn1 <- function(x) x; fn2 <- function(x = 2) y; fn3 <- NULL
expected_params <- list(fn1 = 'x', fn2 = 'y', fn3 = 'x')
.replace_null_fns(env = env_curr, expected_params = expected_params)
fn3 # replaced to have a function with arguments as specified by expected_params
fn2; fn1 # no change in either