bug: fix null pointer in wakeDisplay

[adamshiervani]

I managed to trigger a null pointer in the display.go - this pr prevents this from happening again.

panic: runtime error: invalid memory address or nil pointer dereference
[signal SIGSEGV: segmentation violation code=0x1 addr=0x4 pc=0x141414]

goroutine 3678 [running]:
time.(*Ticker).Reset(0x0, 0x1a3185c5000)
	time/tick.go:69 +0x4c
github.com/jetkvm/kvm.wakeDisplay(0x0, {0xd3cb94, 0x17})
	github.com/jetkvm/kvm/display.go:313 +0x160
github.com/jetkvm/kvm.requestDisplayUpdate.func1()
	github.com/jetkvm/kvm/display.go:188 +0x38
created by github.com/jetkvm/kvm.requestDisplayUpdate in goroutine 3674
	github.com/jetkvm/kvm/display.go:186 +0xb8

When figuring out the issues, I also noticed that the FE is passing stale useState values to the backend. This is now fixed!