An error occurred processing an eval datasource:

<pre>invalid set id: ""</pre>

The error trace was:

<pre>invalid set id: ""
    while executing
"gc_set get {} ope_series_id"
    ("eval" body line 1)
    invoked from within
"eval [concat [list gc_set] $args]"
    ("default" arm line 2)
    invoked from within
"switch $cmd {
	exists {
	    if [catch { ns_set size [snd $args] }] {
		return 0
	    } else {
		return 1
	    }
	}
	keys {
	    ns_set_keys [snd $arg..."
    (procedure "ns_set" line 3)
    invoked from within
"ns_set get [lindex $series_list $series_list_counter] ope_series_id"
    invoked from within
"set current [ns_set get [lindex $series_list $series_list_counter] ope_series_id]"
    ("eval" body line 35)
    invoked from within
"eval $_EVALCONDITION "
    invoked from within
"set series.event_list [eval $_EVALCONDITION ] "
    ("uplevel" body line 2)
    invoked from within
"uplevel #0 { 
      set series.event_list [eval $_EVALCONDITION ] 
      set event_list [set series.event_list]
    }"
    ("eval" body line 1)
    invoked from within
"eval "uplevel #0 { 
      set $varname \[eval \$_EVALCONDITION \] 
      set $name \[set $varname\]
    }" "
    (procedure "ad_template_get_data_eval" line 13)
    invoked from within
"ad_template_get_data_eval $template_name $datasource "
    ("eval" arm line 1)
    invoked from within
"switch $type {

    eval       { ad_template_get_data_eval $template_name $datasource }
    param      { ad_template_get_data_param $template_name $da..."
    (procedure "ad_template_get_data" line 16)
    invoked from within
"ad_template_get_data $name $datasource"
    (procedure "ad_template_get_all_data" line 8)
    invoked from within
"ad_template_get_all_data $spec"
    (procedure "ad_template_init" line 11)
    invoked from within
"ad_template_init url"
    (procedure "ad_template_filter" line 9)
    invoked from within
"ad_template_filter $url"</pre>