Fix Select dropdown border

components/select/style/index.less

@@ -489,6 +489,10 @@
         background-color: @item-hover-bg;
       }
 
+      &:first-child, &:last-child {
+        border-radius: @border-radius-base;
+      }
+
       &-disabled {
         color: @disabled-color;
         cursor: not-allowed;