Why does it really matter? It's one letter, the word hasn't changed drastically.
Also, in this instance, you can't be lazy and ignorant - that doesn't make sense.
In this instance, if you're too lazy to put the extra letter on Viking, then you obviously know it is spelt Vikingr - otherwise you wouldn't be lazy as you don't know.
But this is getting off topic, we shouldn't be talking about laziness, ignorance and the spelling of Vikingr.