[BUG] Modeline shadows don't always get properly redrawn

Reproduce by: $ xrdb < /dev/null $ xemacs-21.0-b39 -vanilla (resize-minibuffer-mode) C-j => t M-x font-lock-mode M-: (set-face-foreground (find-face 'font-lock-comment-face) "magenta4") On the final line hit enough blanks after the closing paren so that the modeline grows to two lines. Then hit return. The comment text turns to magenta4, correct. The modeline shrinks to one line, correct. The modeline shadows don't get redrawn. Uh oh. This bug is also present in XEmacs 20.4.