Menu, Clipboard, import replaces whole content

1. go to https://demo.codimd.org/new
1. insert `first line` in the first line and `last line` in the third line
1. place cursor in the second line and select menu, clipboard
1. insert `second line` and press *import*

The whole content becomes replaced by `second line`. It would be more helpful, if the imported text is inserted at the cursor.