You say half batch, I assume 2.5 gallons?
I prefer to make starters vs. not making them, but in this case I would say it wasn't necessary - White Labs vials have cell counts roughly equivalent to starters in the 1 to 2 liter range. For 2.5 gallons at probably around a 1050 OG, dumping the vial would be fine.
Obviously you've made it already, I would just dump the whole thing in, don't sweat it.
And if worse comes to worse, plan on brewing again and pitching on top of part of that cake in a few weeks.
There's always a silver lining!