Two sentences - articles

I was looking up the definition of the word "wreck" and found these two possible meanings which are not surprising for me, but I was baffled by the use of the articles.

1) (informal) a person who is in a bad physical or mental condition

2) (informal) a vehicle, building, etc. that is in very bad condition

I am asking you why there is an indefinite article in the first sentence whilst the second one has no article?

Thanks a lot.