Fix visibility checks for global alerts.

[duozersk]

If alert is global then the $pages array ends up as [0 => ""] and can't be empty after the preg_split function.

Steps to review:

• create new alert with no visibility limitations
• verify it is visible on frontpage and several other pages

Conversation about this in Slack https://openy.slack.com/archives/C6G4ZTLVC/p1611132731028300

[gundevel]

Can one of the admins verify this patch? Use "o+k to test" or ''t+est this please" for manual build execution.

[podarok]

ok to test

[gundevel]

Build comment file:

Check Open Y Installation Wizard at http://install.openy.cibox.tools/build3064/install.php

---

Test PASSed.
Refer to this link for build results (access rights to CI server needed):
http://openy.cibox.tools:8080/job/PR_BUILDER_COMPOSER/3064/

[gundevel]

Open Y Upgrade Path site check installed at http://upgrade.openy.cibox.tools/build3064/

[gundevel]

Open Y Complete profile installed at http://openy.cibox.tools/build3064/

[gundevel]

Can one of the admins verify this patch? Use "o+k to test" or ''t+est this please" for manual build execution.

[podarok]

that automation thing is sometimes so overautomated....

[duozersk]

Well... somehow after some changes this PR now contains more commits and more changes and doesn't apply to the place where it was applied without issues before... frustrating :(

[duozersk]

Fixed "frustration" by changing the base branch ^^

[gundevel]

Can one of the admins verify this patch? Use "o+k to test" or ''t+est this please" for manual build execution.

[gundevel]

Can one of the admins verify this patch? Use "o+k to test" or ''t+est this please" for manual build execution.

[gundevel]

Can one of the admins verify this patch? Use "o+k to test" or ''t+est this please" for manual build execution.

[gundevel]

Can one of the admins verify this patch? Use "o+k to test" or ''t+est this please" for manual build execution.

[gundevel]

Can one of the admins verify this patch? Use "o+k to test" or ''t+est this please" for manual build execution.

[gundevel]

Can one of the admins verify this patch? Use "o+k to test" or ''t+est this please" for manual build execution.