1 raider went through a nether portal. I pushed him off the edge and right before he died in the lava I went back to the over world. and the kill did not count. I am stuck with 1 raider left sign at the top of my screen

How to recreate: 

start a raid

get a pillager or any other raid member through the portal

push him of the edge 

get back to the over world right before he dies

watch the sign that says Raid - Raiders remaining: 1 

hopelessly stare at the sign and just know you will have to find a brand new village