prompt: restore a workaround for a cursor misplacement bug in ncurses

When making small movements in the lower right corner, ncurses can
get confused about where the cursor actually is -- a double-width
character seems to throw its calculations off.

This addresses https://savannah.gnu.org/bugs/?59808.

Bug existed since version 5.4, commit 39705c60.

src/prompt.c

@@ -407,6 +407,12 @@ void draw_the_promptbar(void)
 
 	wattroff(bottomwin, interface_color_pair[PROMPT_BAR]);
 
+	/* Work around a cursor-misplacement bug -- https://sv.gnu.org/bugs/?59808. */
+	if (ISSET(NO_HELP)) {
+		wmove(bottomwin, 0, 0);
+		wrefresh(bottomwin);
+	}
+
 	/* Place the cursor at the right spot. */
 	column = base + wideness(answer, typing_x);
 	wmove(bottomwin, 0, column - get_statusbar_page_start(base, column));