fix filter.js operator_changed() bugs

assets/javascripts/reporting/filters.js

@@ -54,7 +54,7 @@ Reporting.Filters = {
         field_el.removeAttribute('data-selected');
         $('rm_' + field).value = ""; // reset the value, so the serialized form will not return this filter
       }
-      Reporting.Filters.operator_changed(field, $("operators_" + field));
+      Reporting.Filters.operator_changed(field, $("operators[" + field + "]"));
       Reporting.Filters.display_category($(field_el.getAttribute("data-label")));
     }
   },
@@ -85,7 +85,7 @@ Reporting.Filters = {
 
   change_argument_visibility: function (field, arg_nr) {
     var params, i;
-    params = [$(field + '_arg_1'), $(field + '_arg_2')];
+    params = [$(field + '_arg_1_val'), $(field + '_arg_2_val')];
 
     for (i = 0; i < 2; i += 1) {
       if (params[i] !== null) {