Hi,
I experienced some conflicts between this plugin and the theme used.
The theme’s support told me this: “Actually, the reason for this issue is in this file (wp-content/plugins/popular-widget/_inc/widget.php) it’s something related to having a non-title widget, but I couldn’t go further than that, please inform the plugin author about this issue, he should be able to shed us some light here..”
Could you help me?

Thanks,
Lily