It's probably been partly rewired then, odd the wire to the light wasn't replaced at the the same time? Or maybe its' cause by too many watt in the bulb? 15 W used to be the limit, some lamps could handle 25W, these days I think there are LEDs for most lamps.
I would go for a rewiring if it was my 128. I know I wouldn't use a hand crank that much even though I might get one at some point. A few years a go I handed my 99 in for rewiring and I haven't regretted it since. I kept the original motor, lights and knee controller and they work fine. These days I'm intersted in doing it my self, and there's rewiring diagrams available several places on the web. I have done the same for my 201, which is my main machine.
You machine probably was a hand crank once, because of the large spoked hand wheel and it looks like it's not fitted with a a Singer motor and lamp. Is it something else? Singer had that type of lamp too though.
It's easy to get a hand crank too, it will go on with out any problem. I track parts like this from varous sources on the web, often ebay or other auction sites.