The hyperlink editor only supports single line editing, but if you paste a URL with a preceding lewline character, the editor keeps the new line. This makes the error non-obvious to the user. It is also impossible to remove the newline in the editor because it is a single-line editor, so it does not recognize that the newline is there. Since newlines are not allowed in URLs and in fact break them, my suggestion is to strip newline characters from URLs when pasted.