Error: missing value where TRUE/FALSE needed(Error in if (func.lambda)

During run a special package, I encounter this error

Error in if (func.lambda(lower, X2, df, b = bb) * func.lambda(l.upper,  :
  missing value where TRUE/FALSE needed

main Code is

RMSEAfun <- function (X2, df, N, CI)
{
  bb <- (1 - CI)/2
  lower <- 0
  l.upper <- X2
  u.upper <- max(N, X2 * 5)
  if (func.lambda(lower, X2, df, b = bb) * func.lambda(l.upper,
                                                       X2, df, b = bb) > 0) {
    l.lambda <- 0
  }
  else {
    l.lambda <- uniroot(f = func.lambda, lower = lower, upper = l.upper,
                        X2 = X2, b = bb, df = df)$root
  }
  if (func.lambda(lower, X2, df, b = CI + bb) * func.lambda(u.upper,
                                                            X2, df, b = CI + bb) > 0) {
    u.lambda <- 0
  }
  else {
    u.lambda <- uniroot(f = func.lambda, lower = lower, upper = u.upper,
                        X2 = X2, b = CI + bb, df = df)$root
  }
  return(c(sqrt(l.lambda/(N * df)), sqrt(u.lambda/(N * df))))
}

this code is really vital for me and now I get stuck How can I save my life?