ext4: move 'ix' sanity check to corrent position

stable inclusion
from stable-v4.19.299
commit 23ab419bde8cc2b378bdbf3d518b7a5542665fbe
category: bugfix
bugzilla: https://gitee.com/openeuler/kernel/issues/I8MCB5
CVE: NA

Reference: https://git.kernel.org/pub/scm/linux/kernel/git/stable/linux.git/commit/?id=23ab419bde8cc2b378bdbf3d518b7a5542665fbe



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[ Upstream commit af90a8f4a09ec4a3de20142e37f37205d4687f28 ]

Check 'ix' before it is used.

Fixes: 80e675f9 ("ext4: optimize memmmove lengths in extent/index insertions")
Signed-off-by: Gou Hao <gouhao@uniontech.com>
Link: https://lore.kernel.org/r/20230906013341.7199-1-gouhao@uniontech.com


Signed-off-by: Theodore Ts'o <tytso@mit.edu>
Signed-off-by: Sasha Levin <sashal@kernel.org>
Signed-off-by: Zhang Changzhong <zhangchangzhong@huawei.com>