Rare panic when setting TWCC extension

[m1k1o]

There is a panic that originates from calling SetExtension on header that is nil.

Unfortunately, it happened only once, I don't know what lead to it and I did not have atached debugger to see more of it.

panic: runtime error: invalid memory address or nil pointer dereference
    [signal SIGSEGV: segmentation violation code=0x1 addr=0x0 pc=0xd46aa5]
    goroutine 209875 [running]:
    github.com/pion/rtp.(*Header).SetExtension(0xc001666f00, 0x1, {0xc002db0a4c, 0x2, 0x2})
    	/go/pkg/mod/github.com/pion/rtp@v1.7.13/packet.go:397 +0x4a5
    github.com/pion/interceptor/pkg/twcc.(*HeaderExtensionInterceptor).BindLocalStream.func1(0xc003054401?, {0xc001679200, 0x4a4, 0x5b4}, 0xc000bade88?)
    	/go/pkg/mod/github.com/pion/interceptor@v0.1.12/pkg/twcc/header_extension_interceptor.go:51 +0x9f
    github.com/pion/interceptor.RTPWriterFunc.Write(0xc000badf7c?, 0xc002d77300?, {0xc001679200?, 0xc000badef8?, 0x89d0cf?}, 0xc000901740?)
    	/go/pkg/mod/github.com/pion/interceptor@v0.1.12/interceptor.go:83 +0x31
    github.com/pion/interceptor/pkg/nack.(*ResponderInterceptor).resendPackets.func1(0xb8ef?)