Infinite timeouts don't work

```r
library(simmer)

t <- trajectory() %>%
  timeout(Inf)

simmer() %>%
  add_generator("dummy", t, at(0)) %>%
  run() %>%
  get_mon_arrivals()
#>     name start_time end_time activity_time finished replication
#> 1 dummy0          0        1             1     TRUE           1
```