f2fs: check curseg->inited before write_sum_page in change_curseg

In the __f2fs_init_atgc_curseg->get_atssr_segment calling,
curseg->segno is NULL_SEGNO, indicating that there is no summary
block that needs to be written.

Fixes: 093749e ("f2fs: support age threshold based garbage collection")
Signed-off-by: Yongpeng Yang <yangyongpeng1@oppo.com>
Reviewed-by: Chao Yu <chao@kernel.org>
Signed-off-by: Jaegeuk Kim <jaegeuk@kernel.org>

Author: Yongpeng Yang

fs/f2fs/segment.c

@@ -2926,7 +2926,8 @@ static int change_curseg(struct f2fs_sb_info *sbi, int type)
 	struct f2fs_summary_block *sum_node;
 	struct page *sum_page;
 
-	write_sum_page(sbi, curseg->sum_blk, GET_SUM_BLOCK(sbi, curseg->segno));
+	if (curseg->inited)
+		write_sum_page(sbi, curseg->sum_blk, GET_SUM_BLOCK(sbi, curseg->segno));
 
 	__set_test_and_inuse(sbi, new_segno);