Warnings on update - OJS 3.1.2.1

I’m making some tests for upgrade for the version 3.1.2.1.

When I updated the DB some warnings appeared:

WARNING: The NavigationMenu (ContextId: 1, Title: User Navigation Menu, Area: user) will be skipped because the specified area has already a NavigationMenu attached.

WARNING: The NavigationMenu (ContextId: 1, Title: Primary Navigation Menu, Area: primary) will be skipped because the specified area has already a NavigationMenu attached.

This message appeared again for the contextId 0, 1, 3, 4, 6, 7, 8 and 9.

A notice appeared too:

PHP Notice: Only variables should be assigned by reference in /home/magazine/public_html/lib/pkp/classes/cliTool/UpgradeTool.inc.php on line 97

What is the meaning of this messages ? Can I fix it ?

Hi @rique!

Please take a look at that answer [Error with my custom themes after upgrade to version 3.1.2 - #9 by Dimitris_Efstathiou].

If it does not help, feel free to continue the thread.

thanks!
@Dimitris_Efstathiou