in Create network page, the step page content disappears

[pengyuesheng]

Steps：
1、Click the Create Network button
2、Enter 123 in the Allocation Pools
3、Then click on the created button
4、When the page returns to the Create Network page, click the Back button and then click the Next button, you will find that the page content disappears.

[OpenStack Infra (hudson-openstack)]

Fix proposed to branch: master
Review: https://review.openstack.org/619158

[OpenStack Infra (hudson-openstack)]

Reviewed: https://review.openstack.org/619158
Committed: https://git.openstack.org/cgit/openstack/horizon/commit/?id=0cf4df4a6ffada9c2c4e47a252f881603e045d70
Submitter: Zuul
Branch: master

commit 0cf4df4a6ffada9c2c4e47a252f881603e045d70
Author: pengyuesheng <email address hidden>
Date: Wed Nov 21 15:14:53 2018 +0800

    Check if the alert box has a sibling element, delete its parent if it doesn't exist

    Steps：
    1.Click the Create Network button
    2.Enter 123 in the Allocation Pools
    3.Then click on the Create button
    4.When the page returns to the Create Network page,
    click the Back button and then click the Next button,
    you will find that the page content disappears.

    Change-Id: I6210f6a1ada2826f83aa59318fb48f38da03cb89
    Closes-Bug: #1804374

[OpenStack Infra (hudson-openstack)]

This issue was fixed in the openstack/horizon 15.0.0.0b2 development milestone.