It looks like you have a theme or plugin that is calling one of the WordPress image-related functions with a bad parameter -- using an array instead of a size name (which is a string). This trickles down to the
editor_max_image_size() filter, which should receive a size name as its second parameter, but in your case, it's an array.
You should find the plugin / theme responsible and open a support ticket with them. Just disable each plugin one by one until the problem goes away, and you'll know which one it is.
Meanwhile, I'll add some extra error checking in the next version, but that won't solve your issue - only bypass it.