I dont think that was ever implemented for the group header .. you should be able to easily fix this by editing reportico.php at around line 190 and modifying the function which gets column attributes :-
function & derive_attribute ( $attrib_name, $default )
{
if ( $this->attributes[$attrib_name] )
{
return $this->attributes[$attrib_name];
}
else
{
return $default;
}
}
and change it to something like
function & derive_attribute ( $attrib_name, $default )
{
if ( $this->attributes[$attrib_name] )
{
if ( $this->attributes[$attrib_name] == "BLANK" )
return " ";
else
return $this->attributes[$attrib_name];
}
else
{
return $default;
}
}