[views] csvexport accept an empty rset (closes #4236928) When you tried to apply the 'csvexport' view on an empty rset, the view couldn't be selected and you got a HTTP 500 error. Also add two new test cases.

#! /bin/sh -e
#

if [ "$1" = remove -o "$1" = upgrade ]; then
  if which install-docs >/dev/null 2>&1; then
    install-docs -r cubicweb-doc
  fi
fi

#DEBHELPER#

exit 0