[bugfix] don't return a point for keysign func

Son of Odinrequested to merge
380-issue into master

Closes #380 (closed)

panic: runtime error: invalid memory address or nil pointer dereference
[signal SIGSEGV: segmentation violation code=0x1 addr=0x0 pc=0x10c8f41]

goroutine 98172 [running]:
gitlab.com/thorchain/thornode/bifrost/signer.(*Signer).signAndBroadcast(0xc000b5c420, 0xc002718ca0, 0x3, 0xc000db1b30, 0x2b, 0xc002ccb270, 0x4b, 0x0, 0xc002e2a7e0, 0x1, ...)
	/app/bifrost/signer/sign.go:348 +0x391
gitlab.com/thorchain/thornode/bifrost/signer.(*Signer).processTransactions.func1(0xc002718260, 0xc000b5c420, 0xc003239200, 0x3, 0x4)
	/app/bifrost/signer/sign.go:198 +0x304
created by gitlab.com/thorchain/thornode/bifrost/signer.(*Signer).processTransactions
	/app/bifrost/signer/sign.go:186 +0x134

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