Fixed bug in mg tallying
Fixed bug in mg tallying

bhermanmit/openmc,johnnyliu27/openmc,smharper/openmc,walshjon/openmc,mit-crpg/openmc,walshjon/openmc,amandalund/openmc,walshjon/openmc,wbinventor/openmc,smharper/openmc,wbinventor/openmc,liangjg/openmc,liangjg/openmc,samuelshaner/openmc,johnnyliu27/openmc,amandalund/openmc,paulromano/openmc,shikhar413/openmc,paulromano/openmc,shikhar413/openmc,smharper/openmc,paulromano/openmc,paulromano/openmc,bhermanmit/openmc,johnnyliu27/openmc,samuelshaner/openmc,liangjg/openmc,walshjon/openmc,samuelshaner/openmc,amandalund/openmc,johnnyliu27/openmc,shikhar413/openmc,amandalund/openmc,samuelshaner/openmc,liangjg/openmc,mit-crpg/openmc,mit-crpg/openmc,shikhar413/openmc,mit-crpg/openmc,smharper/openmc,wbinventor/openmc,wbinventor/openmc