multiple PHP errors for Pop Up Pro

While trying to track down the cause of a massive CPU spike earlier today, I found my error logs were full of errors related to PopUp Pro:

2015/08/31 15:54:30 [error] 3737#0: *1986622 FastCGI sent in stderr: "PHP message: PHP Warning:  Invalid argument supplied for foreach() in /var/www/ on line 190

Literally hundreds of these errors during the spike. Too many to count.

Possible someone could take a look and let me know if this is a server conflict or a problem with the plugin itself?