ui/ncurses: Clear remaining space when drawing help line

When drawing the screen's help line clear each character after the new
help line to avoid stale parts of the previous screen's help line
remaining on the screen.

Signed-off-by: Samuel Mendoza-Jonas <sam@mendozajonas.com>

ui/ncurses/nc-scr.c

@@ -56,7 +56,7 @@ int nc_scr_unpost(struct nc_scr *scr)
 
 void nc_scr_frame_draw(struct nc_scr *scr)
 {
-	int ltitle_len, rtitle_len;
+	int ltitle_len, rtitle_len, help_len;
 
 	DBGS("ltitle '%s'\n", scr->frame.ltitle);
 	DBGS("rtitle '%s'\n", scr->frame.rtitle);
@@ -77,6 +77,10 @@ void nc_scr_frame_draw(struct nc_scr *scr)
 
 	mvwhline(scr->main_ncw, LINES - nc_scr_pos_help_sep, 1, ACS_HLINE,
 		COLS - 2);
+	help_len = 1 + strlen(scr->frame.help);
+	if (help_len < COLS)
+		mvwhline(scr->main_ncw, LINES - nc_scr_pos_help, help_len, ' ',
+				COLS - help_len);
 	mvwaddstr(scr->main_ncw, LINES - nc_scr_pos_help, 1, scr->frame.help);
 	nc_scr_status_draw(scr);
 }