Problems: fix trigger name filter

src/datasource-zabbix/partials/query.editor.html

@@ -152,7 +152,7 @@
     <div class="gf-form max-width-20" ng-show="ctrl.target.queryType == editorMode.PROBLEMS">
       <label class="gf-form-label query-keyword width-7">Problem</label>
       <input type="text"
-        ng-model="ctrl.trigger.filter"
+        ng-model="ctrl.target.trigger.filter"
         ng-blur="ctrl.onTargetBlur()"
         placeholder="Problem name"
         class="gf-form-input"