I think it depends on whether the speaker considers good (or stable, critical, or mint) to be an adjective describing condition, or the two-word phrase x condition to be an adjective phrase describing the object. In the former case, an article would be included; in the latter, it is omitted, even though a hyphen isn't being used:
John had a mint-condition 1954 Chevrolet.
So, even though your question asks about the article, it would be related to a question inquiring about the hyphen. In this case, I can find instances of both in print literature:
A mint condition card is flawless, with no nicks, cuts, stains, creases, scratches, or offcentering. (Collecting Basketball Cards: A Complete Guide with Prices, 2000)
A mint-condition baseball signed by Babe Ruth and Lou Gehrig sold at auction last year for more than $68,000. (Kiplinger's Personal Finance, Mar 2000)
If you're interested, you can read more about the very-vexing hyphenation convention problem at this ELU answer.