Update index.html

Author: bmarkov

Diff for: demos/tree/dropdownmode/src/index.html

@@ -18,6 +18,11 @@
       format("truetype");
   font-weight: normal;
   font-style: normal;
+}
+.smart-tree-popup {
+  position: absolute;
+  border: none;
+  height: 300px;
 }
   </style>
   <script>