Get proper indices for zero flux error
Get proper indices for zero flux error

walshjon/openmc,amandalund/openmc,mit-crpg/openmc,mit-crpg/openmc,smharper/openmc,liangjg/openmc,paulromano/openmc,liangjg/openmc,amandalund/openmc,mit-crpg/openmc,liangjg/openmc,smharper/openmc,shikhar413/openmc,paulromano/openmc,shikhar413/openmc,walshjon/openmc,paulromano/openmc,paulromano/openmc,liangjg/openmc,shikhar413/openmc,smharper/openmc,shikhar413/openmc,walshjon/openmc,mit-crpg/openmc,amandalund/openmc,amandalund/openmc,smharper/openmc,walshjon/openmc