checkMesh reports negative internal points

• take multiRegionHeater tutorial
• comment out regions in decomposeParDict, i.e. use scotch for decomposition

mpirun -np 4 checkMesh -region heater -parallel

produces

    internal points:  -2
--> FOAM Warning : 
    From function void Foam::printMeshStats(const Foam::polyMesh&, bool)
    in file checkTools.C at line 66