Fix templatig issue, when no values returned, closes #354

src/datasource-zabbix/datasource.js

@@ -314,7 +314,7 @@ class ZabbixAPIDatasource {
     }
 
     return result.then(metrics => {
-      return metrics.map(formatMetric);
+      return _.map(metrics, formatMetric);
     });
   }
 

src/datasource-zabbix/zabbix.js

@@ -165,14 +165,14 @@ angular
  * Find group, host, app or item by given name.
  * @param  list list of groups, apps or other
  * @param  name visible name
- * @return      array with finded element or undefined
+ * @return      array with finded element or empty array
  */
 function findByName(list, name) {
   var finded = _.find(list, {'name': name});
   if (finded) {
     return [finded];
   } else {
-    return undefined;
+    return [];
   }
 }
 
@@ -182,14 +182,14 @@ function findByName(list, name) {
  * which return only first finded.
  * @param  {[type]} list list of elements
  * @param  {[type]} name app name
- * @return {[type]}      array with finded element or undefined
+ * @return {[type]}      array with finded element or empty array
  */
 function filterByName(list, name) {
   var finded = _.filter(list, {'name': name});
   if (finded) {
     return finded;
   } else {
-    return undefined;
+    return [];
   }
 }