Bug-fix:  work around for a bug in petsc that pops up with intel 15.
Bug-fix:  work around for a bug in petsc that pops up with intel 15.

VecGetValues fails a check when passing it a zero-length array. This is fixed in petsc master 18ae1927.

rjferrier/fluidity,rjferrier/fluidity,jrper/fluidity,jrper/fluidity,jjo31/ATHAM-Fluidity,iakovos-panourgias/fluidity,jjo31/ATHAM-Fluidity,jrper/fluidity,iakovos-panourgias/fluidity,jjo31/ATHAM-Fluidity,jjo31/ATHAM-Fluidity,jrper/fluidity,iakovos-panourgias/fluidity,jrper/fluidity,rjferrier/fluidity,iakovos-panourgias/fluidity,iakovos-panourgias/fluidity,jjo31/ATHAM-Fluidity,rjferrier/fluidity,rjferrier/fluidity