[hackers] [dmenu] fix UB with the function iscntrl() || Hiltjo Posthuma

[git]

commit e73651f12a406629778f02d8e5acbe2caec0dfc2
Author:     Hiltjo Posthuma <hil...@codemadness.org>
AuthorDate: Sat Mar 26 17:58:47 2022 +0100
Commit:     Hiltjo Posthuma <hil...@codemadness.org>
CommitDate: Sat Mar 26 17:58:47 2022 +0100

    fix UB with the function iscntrl()
    
    From commit 6818e07291f3b2913e687c8ec3d3fe4711724050 by NRK, thanks

diff --git a/dmenu.c b/dmenu.c
index 085dc29..839f6cc 100644
--- a/dmenu.c
+++ b/dmenu.c
@@ -415,7 +415,7 @@ keypress(XKeyEvent *ev)
        switch(ksym) {
        default:
 insert:
-               if (!iscntrl(*buf))
+               if (!iscntrl((unsigned char)*buf))
                        insert(buf, len);
                break;
        case XK_Delete: