Fixed broken examples by adding NULL after stess/atom commands

examples/USER/atc/elastic/in.bar1d_flux

examples/USER/atc/elastic/in.bar1d_ghost_flux

examples/USER/atc/elastic/in.bar1d_thermo_elastic

examples/USER/awpmd/H/in.h_atom

examples/USER/awpmd/H/in.h_molecule

examples/USER/eff/ECP/Si2H6/in.Si2H6

examples/USER/eff/ECP/Si2H6/in.Si2H6.ang

examples/USER/eff/ECP/SiH4/in.SiH4

examples/USER/eff/ECP/SiH4/in.SiH4.ang

examples/USER/eff/H/in.h_atom.spe.ang

examples/USER/eff/H/in.h_atom.spe.bohr

examples/USER/eff/H2/in.h2

examples/USER/eff/H_plasma/in.h2bulk.nve.ang

examples/USER/eff/Li-solid/in.Li.ang

examples/USER/eff/Li-solid/in.Li.bohr

examples/USER/eff/fixed-core/C2H6/in.C2H6fc.ang

examples/USER/eff/fixed-core/C2H6/in.C2H6fc.bohr

examples/USER/eff/fixed-core/CH4/in.CH4fc.ang

examples/USER/eff/fixed-core/CH4/in.CH4fc.bohr

examples/USER/eff/fixed-core/CH4/in.CH4fc.spe.ang