Logo disappeared after modification

Hello,
I installed the demo version of kickoff template and after changing the logo, it disappeared from frontend. I got this message:
Warning: explode () expects parameter 2 to be string, array GIVEN in /templates/mysite/yjsgcore/lib/yjsg_loadgrids.php on line 247

Warning: array_key_exists () expects parameter 2 to be array, null GIVEN in /templates/mysite/yjsgcore/lib/yjsg_loadgrids.php on line 254

I made the following update:

I replaced the line:
$ Grid_widths = explode ('|', $ Document,> params-> get ($ get_w_param));
with:
if (is_array ($ Document,> params-> get ($ get_w_param)))
$ Document, $ grid_widths => params-> get ($ get_w_param);
else
$ Grid_widths = explode ('|', $ Document,> params-> get ($ get_w_param));

which led to the disappearance of the error message BUT the logo has not returned.
Please give me a suggestion.
Thank you!

Are you sure your are posting in product assigned forum?: Yes

What is your CMS version?: Joomla 3.x

MySQL Version: 5.x

PHP version: 5.x

Link to installation: localhost

Have you edited any files? If yes tell us which ones.: Yes

Is this personal or client website?: Personal

Hello bemyfriend.
Please download the latest plugin version and just re-install it, after that check your logo.
http://www.youjoomla.com/joomla-exte...rk-plugin.html

Here's what has happened:
I reinstalled the plugin YJSG. The website completely disappeared in frontend and I received the following message:
">
Warning: require (C: \ xampp \ htdocs \ rasoomdemo \ plugins \ system \ yjsg \ layouts / yjsg_topmenu.php): failed to open stream: no such file or directory in C: \ xampp \ htdocs \ rasoomdemo \ Templates \ kickoff \ layouts \ yjsg_headerblock_custom.php on line 31

Fatal error: require (): Failed opening required 'C: \ xampp \ htdocs \ rasoomdemo \ plugins \ system \ yjsg \ layouts / yjsg_topmenu.php' (include_path = 'C: \ xampp \ php \ PEAR') in C: \ xampp \ htdocs \ rasoomdemo \ templates \ kickoff \ layouts \ yjsg_headerblock_custom.php on line 31

I rebuilt the site from backup made to the installation of the plugin and from that moment I was able to change the logo, but the following message appeared in frontend:

Warning
JUser:: _load: Unable to load user with ID: 42

and in the backend:

Warning
You are Using templates pre plugin version. Go to YJSG plugin to update.

So I can change the logo as I want, but these two messages appear. Now I want to understand why I get this message in frontend and how to get rid of it?
Thank You!

Hello bemyfriend.
Please notice that you are using old template and framework version.
You should install the latest template and plugin framework version so it can be compatible with the latest updates.
http://www.youjoomla.com/yjsg-framew...-released.html
http://www.youjoomla.com/joomla_supp...ad.php?t=12890

As for JUser warning, you need to update your SQL for K2 tables.

UPDATE prefix_k2_items SET created_by = user_ID WHERE created_by = 42
UPDATE prefix_k2_items SET modified_by = user_ID WHERE modified_by = 42

prefix - table prefix
user id - your current user_ID