On Safari OSX when printing a pdf the first call to Print.js always shows a blank page. Subsequent calls work fine.

I am on Safari 14.0.3 (OSX) and printjs 1.6.0.

I call printjs like so:
```
printJS({
printable: url,
type: 'pdf'
})
```

The first time I do this, the print dialog opens, but it always shows a blank page.

I close the print dialog and try again.

Now Safari shows an alert "This webpage is trying to print. Do you want to print this webpage?" This alert did not appear on the first try. I click "yes" and everything now works as expected.

So it is just the the first call to printjs that is not working correctly.