Character Save Error

I am unsure whether this has been answered before, but if it was I couldn't find it. The jist is rarely (but at extremely inconvenient times) my game would crash, citing the error attached. I have also attached a log that ends with the crash. I am unsure of how to cause it, as it rarely and randomly happens. I only have one instance of Terraria open, if that helps. Thanks in advance!

client.log