fix "block with unknown header is ready" error

[noot]

Task summary

• when syncing on the devnet, the error "block with unknown header is ready" shows up somewhat often
• this really shouldn't be happening, as this means the handleReadyBlock function is being called with a block that isn't ready (ie. it's header isn't available to us)
• the error is probably coming from tipSyncer.handleTick, as when handleReadyBlock is called from doSync, the block data is verified to already have headers

[noot]

update: this seems to happen from the doSync call, and the block was already put into the ready queue before this happens??

2022-01-12T19:21:17Z INFO handling block response block Hash=0x3e430f7e182a44e516584c1abbaa91c796c5ec9674d551f82d4e6d5048f0b0c1 Header=ParentHash=0x2fa7cf7d28c02449037ddd7f27e83997a6e627670de5b5b50771bebdf2c2ff90 Number=1587 StateRoot=0x59b5a68efd471932c57d1c4f29a11e8eb5a3da050d161b2e19a3275eb8113fd9 ExtrinsicsRoot=0x06b0868f5fe51b61e18742d238b936f0ac2829a67ed5179a59c99bc348cafe8d Digest={{<nil> map[2:{[0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0]} 4:{[0 0 0 0] []} 5:{[0 0 0 0] []} 6:{[0 0 0 0] []}]} [{{[66 65 66 69] [1 1 0 0 0 183 184 159 32 0 0 0 0 106 203 100 35 186 224 125 218 203 129 91 50 149 9 149 23 76 92 114 63 109 57 62 39 180 160 178 84 102 219 73 40 100 69 66 205 159 76 89 126 185 177 11 168 131 152 98 226 22 34 38 60 0 182 153 184 187 101 60 214 90 237 37 12 204 75 27 142 217 221 25 79 55 88 97 178 193 237 10 224 19 161 90 165 81 108 22 123 93 103 199 183 45 205 172 4]} map[2:{[0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0]} 4:{[0 0 0 0] []} 5:{[0 0 0 0] []} 6:{[0 0 0 0] []}]} {{[66 65 66 69] [40 176 211 177 240 152 222 64 249 120 48 174 231 102 112 44 219 175 114 66 164 1 3 44 128 34 42 242 152 116 185 87 16 253 21 199 252 13 222 115 246 23 72 207 141 121 76 107 52 18 78 188 128 187 232 165 8 209 106 47 16 202 163 134]} map[2:{[0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0]} 4:{[0 0 0 0] []} 5:{[0 0 0 0] []} 6:{[0 0 0 0] []}]}]} Hash=0x3e430f7e182a44e516584c1abbaa91c796c5ec9674d551f82d4e6d5048f0b0c1 Body=[0x0403000b8da0bc4f7e01] 	chain_sync.go:L695	pkg=sync
2022-01-12T19:21:17Z INFO handling block response block Hash=0x3e430f7e182a44e516584c1abbaa91c796c5ec9674d551f82d4e6d5048f0b0c1 Body=[0x0403000b8da0bc4f7e01] 	chain_sync.go:L695	pkg=sync
2022-01-12T19:21:17Z CRIT block with  unknown header is ready: hash=0x3e430f7e182a44e516584c1abbaa91c796c5ec9674d551f82d4e6d5048f0b0c1	chain_sync.go:L713	pkg=sync