I get the same issue, but I’d just remove the time output for now – so delete the code that says:
{$before_timesince}<a href=\"" . esc_url( "https://twitter.com/{$account}/statuses/{$tweet_id}" ) . '" class="timesince">' . str_replace(' ', ' ', wpcom_time_since(strtotime($tweet['created_at']))) . " ago</a>
from line 175 of the wickett-twitter-widget.php file in your plug-in editor as Niall suggests.
