File vim-8.0.1568-CVE-2021-3928.patch of Package vim.23083

--- vim-8.0.1568.orig/src/spell.c	2022-02-03 20:50:13.629648897 +0200
+++ vim-8.0.1568/src/spell.c	2022-02-17 19:25:14.214324959 +0200
@@ -4715,7 +4715,7 @@
 		     * char, e.g., "thes," -> "these". */
 		    p = fword + sp->ts_fidx;
 		    MB_PTR_BACK(fword, p);
-		    if (!spell_iswordp(p, curwin))
+		    if (!spell_iswordp(p, curwin) && *preword != NUL)
 		    {
 			p = preword + STRLEN(preword);
 			MB_PTR_BACK(preword, p);