Term filter causes solr 500 error (patch included)

Hi,

if you add and exposed filter of a taxonomy term (i suppose that whatever integer value is affected), and you dont give a value an invalid solr query is constructed and solr gives an error.

here is a log of the query: im_field_obra_clasificaciongener:()) is wrong.

INFO: [] webapp=/solr path=/select params={f.im_field_obra_clasificaciongener.facet.limit=50&f.bm_field_obra_adquisicion_recien.facet.mincount=1&facet=true&f.itm_field_obra_datacion_1.facet.mincount=1&facet.mincount=1&f.im_field_obra_clasificaciongener.facet.mincount=0&qf=taxonomy_names^2.0&qf=label^5.0&qf=content^40&qf=tos_content_extra^0.1&qf=tos_name^3.0&f.itm_field_obra_datacion_1.facet.limit=50&q.alt=(bundle:(obra)+AND+im_field_obra_clasificaciongener:())&json.nl=map&f.itm_field_obra_anio_ingreso.facet.mincount=1&wt=json&rows=10&fl=id,entity_id,ts_snippet&f.itm_field_obra_anio_ingreso.facet.limit=50&facet.sort=count&start=0&q=&f.bm_field_obra_adquisicion_recien.facet.limit=50&facet.field=itm_field_obra_anio_ingreso&facet.field={!ex%3Dim_field_obra_clasificaciongener}im_field_obra_clasificaciongener&facet.field=bm_field_obra_adquisicion_recien&facet.field={!ex%3Ditm_field_obra_datacion_1}itm_field_obra_datacion_1} status=400 QTime=3

It seens that the apachesolr_views_handler_filter class is not asking for the right value to check if it is empty.

In the following code snippet $this->value is an Array (at least when a taxonomy is used), so we must check for empty($this->value[0])

class apachesolr_views_handler_filter extends views_handler_filter {
  function query() {
    if (!empty($this->value)) {
      if (is_array($this->value)) {
        $this->value = implode(' OR ', $this->value);
      }
      $this->query->add_where($this->options['group'], "$this->real_field", $this->value, $this->operator);
    }
  }

I send a patch in a moments.

Best
David