Fixed bug where no surface current tallies caused segfault.
Fixed bug where no surface current tallies caused segfault.

shikhar413/openmc,sxds/opemmc,amandalund/openmc,mit-crpg/openmc,kellyrowland/openmc,johnnyliu27/openmc,walshjon/openmc,keadyk/openmc_mg_prepush,samuelshaner/openmc,paulromano/openmc,mit-crpg/openmc,nhorelik/openmc,wbinventor/openmc,liangjg/openmc,wbinventor/openmc,paulromano/openmc,samuelshaner/openmc,bhermanmit/openmc,smharper/openmc,keadyk/openmc_mg_prepush,mit-crpg/openmc,johnnyliu27/openmc,wbinventor/openmc,mjlong/openmc,wbinventor/openmc,keadyk/openmc_mg_prepush,johnnyliu27/openmc,sxds/opemmc,paulromano/openmc,lilulu/openmc,lilulu/openmc,smharper/openmc,liangjg/openmc,johnnyliu27/openmc,amandalund/openmc,nhorelik/openmc,shenqicang/openmc,shikhar413/openmc,paulromano/openmc,liangjg/openmc,shenqicang/openmc,smharper/openmc,liangjg/openmc,lilulu/openmc,amandalund/openmc,mjlong/openmc,kellyrowland/openmc,shikhar413/openmc,bhermanmit/openmc,shikhar413/openmc,walshjon/openmc,walshjon/openmc,samuelshaner/openmc,bhermanmit/cdash,samuelshaner/openmc,mit-crpg/openmc,amandalund/openmc,walshjon/openmc,smharper/openmc