Wilcity Theme Options based on Redux Framework and the above issue is causing by Redux Core.

We found where is causing this bug and We reported it to Redux author.

You can now temporary resolve it by uploading https://www.dropbox.com/s/igi15xq9zs67djy/class-redux-wordpress-data.php?dl=0 to wp-content -> plugins -> redux-framework -> redux-core -> inc -> classes folder.