Altria's cigarette business is suffering huge volume declines, yet investors continue to push the stock higher.Altria (MO -1.21%) is basically a one-trick pony when it comes to what it sells. Combustible tobacco products -- largely cigarettes -- make up roughly 88% of its top line. This had long been viewed as a problem by investors, but recently, some small positives have left investors willing to overlook the very real problems Altria continues to face.Altria's biggest problem hasn't changedCigarette sale ...