bug: drag-left cursor at word[0], drags left neighbour word

[rhoit]

When you try to drag word when cursor at first char of a word, it drags the left neighbour word

illustration: (assuming bold face is the place where cursor is.

word1 word2 word3 word4
after M-<left>
word2 word1 word3 word4

[duianto]

Confirmed.

cursor = []
M-<left> (drag-stuff-left)

Before:	word1 word2 [w]ord3 word4
After:	[w]ord2 word1 word3 word4
Expected:	word1 [w]ord3 word2 word4

It works as expected from the second to the last character in a word.
For example:

Before:	word1 word2 w[o]rd3 word4
After:	word1 w[o]rd3 word2 word4

System Info

drag-stuff-20161108.749
GNU Emacs 27.1 (build 1, x86_64-w64-mingw32) of 2020-08-21
Windows 10 Version 2004 (OS Build 19041.804)