Error in sidebar

I am seeing this error in the sidebar :

! ) Warning: Invalid argument supplied for foreach() in F:\wamp\www\carol\wp-content\plugins\gk-tabs\gk-tabs.php on line 349
Call Stack
# Time Memory Function Location
1 0.0006 244584 {main}( ) ..\index.php:0
2 0.0011 247656 require( 'F:\wamp\www\carol\wp-blog-header.php' ) ..\index.php:17
3 0.6395 38355000 require_once( 'F:\wamp\www\carol\wp-includes\template-loader.php' ) ..\wp-blog-header.php:16
4 0.6511 38617144 include( 'F:\wamp\www\carol\wp-content\themes\John\single.php' ) ..\template-loader.php:75
5 0.8002 38914384 gk_load( ) ..\single.php:28
6 0.8011 38941128 include( 'F:\wamp\www\carol\wp-content\themes\John\layouts\after.php' ) ..\helpers.layout.php:33
7 0.8042 38948400 gk_dynamic_sidebar( ) ..\after.php:35
8 0.8208 39009824 call_user_func_array:{F:\wamp\www\carol\wp-content\themes\John\gavern\helpers\helpers.layout.php:980} ( ) ..\helpers.layout.php:980
9 0.8208 39010400 WP_Widget->display_callback( ) ..\helpers.layout.php:980
10 0.8210 39015480 Gk_Tabs_Widget->widget( ) ..\widgets.php:344

Thanks very much for your help.
Chris

Hi,

Could you please provide me with your website FTP and back-end access via PM (click the “Private Message” text underneath my avatar) so that I may analyze it?

Piotr,
The website is hosted on my computer. I'm using wamp at the moment. Maybe we can do a teamviewer session if we can arrange it?

Chris

Unfortunately it's not possible, you can upload your website into any temporary (free) server, then I'll be able to check it.