Good call. There's a specific safety warning for this exact situation, related to the water heater.
FIX: If the hot water in the home hasn't been used for two or more weeks, you need to clear the lines. Go to a faucet far from the water heater (like a bathroom sink) and turn on the hot water. Let it run for a few minutes. This vents any potentially explosive hydrogen gas that can build up in an idle water heater system.
IF THAT DIDN'T WORK: After addressing the water heater, give the dishwasher itself a visual check. Make sure all enclosure panels are properly in place and that there's no debris in the bottom of the tub.
HEADS UP: Never store or use combustible materials like gasoline or other flammable liquids or vapors in the vicinity of the dishwasher.