Fix y offset of mouse if status at top. GitHub issue 4738 from Michael

Grant.

screen-redraw.c

@@ -1028,6 +1028,11 @@ screen_redraw_draw_scrollbar(struct screen_redraw_ctx *ctx,
 	int			 sx = ctx->sx, sy = ctx->sy, xoff = wp->xoff;
 	int			 yoff = wp->yoff;
 
+	if (ctx->statustop) {
+		sb_y += ctx->statuslines;
+		sy += ctx->statuslines;
+	}
+
 	/* Set up style for slider. */
 	gc = sb_style->gc;
 	memcpy(&slgc, &gc, sizeof slgc);