PHP Notice: Undefined property: ProSites::$plugin_file in /pro-sites/pro-sites.php on line 115

Hi,

Recently moved the multisite to new server.

1) In one of the themes its giving error

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PHP Notice: Undefined property: ProSites::$plugin_file in /public_html/wp-content/plugins/pro-sites/pro-sites.php on line 115

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Other themes are working fine.

This link is not much of help.

Where can it go wrong?. Please Help.

Thanks