SPRINGFIELD — A pay dispute over a Statehouse construction project that got all wet has been thrown out by an appellate panel. Now, lawyers for the construction firm say the decision could leave state vendors out to dry. The 4th District Appellate Court on Wednesday dismissed a mandamus action brought by a Springfield-based construction company that claimed the state signed off on its work — fireproofing steel in the west attic of the Statehouse in 2011 — but illegally withheld the paycheck worth …