This fixes panics that happen because the handlers assume the user is logged
in when the command is executed.
Example of a panic that happened:
panic: runtime error: invalid memory address or nil pointer dereference
[signal SIGSEGV: segmentation violation code=0x1 addr=0x0 pc=0x928d7c]
goroutine 127 [running]:
main.(*CommandHandler).CommandList(0xc0001783c0, 0xc00016bef8)
/build/commands.go:186 +0x6c
main.(*CommandHandler).Handle(0xc0001783c0, 0xc000455920, 0x1b,
0xc0002480c0, 0xc000250470, 0x4)
/build/commands.go:89 +0x1f3
main.(*MatrixHandler).HandleMessage(0xc000176db0, 0xc0001ae6c0)
/build/matrix.go:161 +0x203
created by maunium.net/go/mautrix-appservice.(*EventProcessor).Start
