Update src/distribution.cpp
Update src/distribution.cpp

Co-authored-by: Paul Romano <a436801bae4f27296736e9545e95ef593e23fd3e@gmail.com>
amandalund/openmc,walshjon/openmc,walshjon/openmc,amandalund/openmc,walshjon/openmc,amandalund/openmc,walshjon/openmc,amandalund/openmc