kOmegaSSTLM: edited delta to avoid floating point exception

[CodeHesed]

In some cases (e.g. airfoil with non zero AoA), floating point exception occurs due to zero values in delta of kOmegaSSTLM.
added max function to the Omega part of delta such that delta will change zero values into a small value.

[CodeHesed]

Example of error message:

#0  Foam::error::printStack(Foam::Ostream&) at ??:?
#1  Foam::sigFpe::sigHandler(int) at ??:?
#2  ? in "/lib/x86_64-linux-gnu/libc.so.6"
#3  Foam::divide(Foam::Field<double>&, Foam::UList<double> const&, Foam::UList<double> const&) at ??:?
#4  Foam::tmp<Foam::DimensionedField<double, Foam::volMesh> > Foam::operator/<Foam::volMesh>(Foam::DimensionedField<double, Foam::volMesh> const&, Foam::DimensionedField<double, Foam::volMesh> const&) at ??:?
#5  Foam::RASModels::kOmegaSSTLM<Foam::CompressibleMomentumTransportModel<Foam::dynamicTransportModel> >::Fthetat(Foam::DimensionedField<double, Foam::volMesh> const&, Foam::DimensionedField<double, Foam::volMesh> const&, Foam::DimensionedField<double, Foam::volMesh> const&) const at ??:?
	#6  Foam::RASModels::kOmegaSSTLM<Foam::CompressibleMomentumTransportModel<Foam::dynamicTransportModel> >::correctReThetatGammaInt() at ??:?
#7  Foam::RASModels::kOmegaSSTLM<Foam::CompressibleMomentumTransportModel<Foam::dynamicTransportModel> >::correct() at ??:?
#8  ? in "/opt/openfoam9/platforms/linux64GccDPInt32Opt/bin/rhoPimpleFoam"
#9  __libc_start_main in "/lib/x86_64-linux-gnu/libc.so.6"
#10  ? in "/opt/openfoam9/platforms/linux64GccDPInt32Opt/bin/rhoPimpleFoam"
Floating point exception