Avoid warnings from FALSE part of ifelse()

I created a user function that computes Hedges' c() bias correction for g (Hedges, 1981). It is directly based on metafor::.cmicalc() function from library(metafor). It does this:

hedges_c <- function(df) {
  return(exp(lgamma(df / 2) - log(sqrt(df / 2)) - lgamma((df - 1)/2)))
}

When applied to a vector containing values <= 1, lgamma() generates a warning, because lgamma(0) generates NaN. So, my solution (and also what metafor::.cmicalc() does) was including an ifelse() statement:

hedges_c <- function(df) {
  cdf <- ifelse(df <= 1, 
                NA,
                exp(lgamma(df / 2) - log(sqrt(df / 2)) - lgamma((df - 1)/2)))
  return(cdf)
}

But, and here is the problem I don't seem to find the solution to, it still generates the warnings(), even if all the values are correctly rendered as NA.

Example:

hedges_c(c(0, 0, 20, 14, 0, 0, 0, 0))
#[1]      NA      NA 0.9619445 0.9452877      NA      NA      NA      NA
#Warning messages:
#1: In ifelse(df <= 1, NA, exp(lgamma(df/2) - log(sqrt(df/2)) - lgamma((df -  :
#  value out of range in 'lgamma'
#2: In ifelse(df <= 1, NA, exp(lgamma(df/2) - log(sqrt(df/2)) - lgamma((df -  :
#  value out of range in 'lgamma'
#3: In ifelse(df <= 1, NA, exp(lgamma(df/2) - log(sqrt(df/2)) - lgamma((df -  :
#  value out of range in 'lgamma'
#4: In ifelse(df <= 1, NA, exp(lgamma(df/2) - log(sqrt(df/2)) - lgamma((df -  :
#  value out of range in 'lgamma'
#5: In ifelse(df <= 1, NA, exp(lgamma(df/2) - log(sqrt(df/2)) - lgamma((df -  :
#  value out of range in 'lgamma'
#6: In ifelse(df <= 1, NA, exp(lgamma(df/2) - log(sqrt(df/2)) - lgamma((df -  :
#  value out of range in 'lgamma'

I understand (e.g., from enter link description here) that the third (FALSE) argument of ifelse() is evaluated even when the condition is TRUE (and inversely if I change the order of the condition and the arguments)... But I simply don't know how to solve that (except maybe for hiding warnings before and after...).