ggsurvplot doesn't work when 'fun' argument is an arbitrary function


```r
library("survival")
fit1 <- survfit(Surv(time, status) ~ sex, data = lung)
ggsurvplot(fit1, data = lung, 
           fun =  function(y) y*100)
```

Error:

Error in switch(fun, log = "log(Survival probability)", event = "Cumulative event",  : 
  EXPR should be a vector of length 1
