In Theme Options -> General -> Layout Width
You must have accidentally “removed” the selection, this is the reason why it’s causing fatal error.
I have made a selection, now it’s loading properly.
Please also make sure Theme Options -> General -> Layout Style is selected. I have selected boxed layout, you can change to wide layout.
For Theme Options that are dropdown, Please check that you have made a selection, it should not be “removed” by clicking on the “cross” sign.