Avoid `undefined` value in select traits

src/trait_manager/view/TraitSelectView.js

@@ -35,7 +35,10 @@ module.exports = TraitView.extend({
           value = el;
         } else {
           name = el.name ? el.name : el.value;
-          value = `${el.value || el.id}`.replace(/"/g, '"');
+          value = `${isUndefined(el.value) ? el.id : el.value}`.replace(
+            /"/g,
+            '"'
+          );
           style = el.style ? el.style.replace(/"/g, '"') : '';
           attrs += style ? ` style="${style}"` : '';
         }

src/trait_manager/view/TraitView.js

@@ -107,7 +107,7 @@ module.exports = Backbone.View.extend({
       const value = this.getModelValue();
       const input = $(`<input type="${type}" placeholder="${plh}">`);
 
-      if (value) {
+      if (!isUndefined(value)) {
         md.set({ value }, { silent: true });
         input.prop('value', value);
       }