White screen of death after trying to change header logo

I’ve manage to white screen my whole website: www.faithhopeandsunshine.com after going into:

Appearance - customise - header - header logo - upload image

I have another website with the host which is fine so I know it’s not an issue with them :o/

I did get this error message during the process:

Help please!!!

Have you checked the server error log? When there’s a white screen, something should be logged that will point to the cause.