prevent creation of filter rules matching no feeds

js/form/ValidationMultiSelect.js

@@ -0,0 +1,20 @@
+/* global define */
+
+// only supports required for the time being
+// TODO: maybe show dojo native error message? i dunno
+define(["dojo/_base/declare", "dojo/_base/lang", "dijit/form/MultiSelect", ],
+    function(declare, lang, MultiSelect) {
+
+        return declare('fox.form.ValidationMultiSelect', [MultiSelect], {
+            constructor: function(params){
+                this.constraints = {};
+                this.baseClass += ' dijitValidationMultiSelect';
+            },
+            validate: function(/*Boolean*/ isFocused){
+                if (this.required && this.attr('value').length == 0)
+                    return false;
+
+                return true;
+            },
+        })
+    });