[material][fluidsystems] specialize getMainComponent for H2OHeavyOil
The base-class default simply returns the phase index. Specialize and return a valid component index also for the gas phase.
Fixes dumux-lecture#10 (closed).
The base-class default simply returns the phase index. Specialize and return a valid component index also for the gas phase.
Fixes dumux-lecture#10 (closed).