[v2.7.0-beta] panic: runtime error: invalid memory address or nil pointer dereference

root@xdc-testnet-2:/home/ubuntu# docker exec -it xdc bash
2bc3d8a3ae11:/work# XDC --version
XDC version 2.7.0-testnet-b1566012

INFO [05-12|13:42:03.640] Block synchronisation started
INFO [05-12|13:42:09.844] Allocated fast sync bloom                size=1024.00KiB
INFO [05-12|13:42:09.844] Initialized fast sync bloom              items=0 errorrate=0.000 elapsed="1.683µs"
INFO [05-12|13:42:10.901] Imported new state entries               count=211 elapsed="2.084µs" processed=8787 pending=3366 retry=0 duplicate=0 unexpected=0
INFO [05-12|13:42:12.626] Imported new state entries               count=619 elapsed="100.329µs" processed=9406 pending=6279 retry=0 duplicate=0 unexpected=0
INFO [05-12|13:42:12.894] Imported new state entries               count=353 elapsed="436.915µs" processed=9759 pending=6484 retry=0 duplicate=0 unexpected=0
INFO [05-12|13:42:12.967] Imported new state entries               count=142 elapsed="305.437µs" processed=9901 pending=6548 retry=0 duplicate=0 unexpected=0
INFO [05-12|13:42:13.083] [HookPenalty] Find a node do not create any block addr=xdc1A1b58D133eFFb6BA1631dA7297D8CD58f65FA73
INFO [05-12|13:42:13.083] [HookPenalty] Find a node do not create any block addr=xdcB5e5acAb644DCbdf64103af723be8D62CCEc76f4
INFO [05-12|13:42:13.083] [HookPenalty] get previous penalty node and add into comeback list addr=xdc8d9532faf1690DD03B4822b6953052FE597231a6
INFO [05-12|13:42:13.083] [HookPenalty] get previous penalty node and add into comeback list addr=xdc93EeA33bc34371Ad5fe0e5741199BF8e038aD19b
INFO [05-12|13:42:13.083] [HookPenalty] get previous penalty node and add into comeback list addr=xdceBB849CFe83c46C68bA4C2D6F07a16bCa991ea79
INFO [05-12|13:42:13.083] [HookPenalty] get previous penalty node and add into comeback list addr=xdcCe04AE211D19b8138C7783964aaa1F7ADdd22275
INFO [05-12|13:42:13.083] [HookPenalty] get previous penalty node and add into comeback list addr=xdc32fB028453207699d7C15BB66377BCf9B29fB0fc
INFO [05-12|13:42:13.083] [HookPenalty] get previous penalty node and add into comeback list addr=xdcFCDcD51159092E923a3011F626F99228923830F1
INFO [05-12|13:42:13.083] [HookPenalty] get previous penalty node and add into comeback list addr=xdc11e75CFf00B1E9e9a7c8B3d069E908713Ed3e049
INFO [05-12|13:42:13.083] [HookPenalty] get previous penalty node and add into comeback list addr=xdc8EbE9B0CE09105714E6a006d751fAF45C435570b
INFO [05-12|13:42:13.083] [HookPenalty] get previous penalty node and add into comeback list addr=xdcD03da188Bb791eF1DFc7638302B51A6a30EE83fc
INFO [05-12|13:42:13.083] [HookPenalty] get previous penalty node and add into comeback list addr=xdc20aE82dC469De249C6814Af6c71f5617621fE92D
INFO [05-12|13:42:13.083] [HookPenalty] get previous penalty node and add into comeback list addr=xdc42e490E0c04F1be8c8cb9b76f630BF97F662169D
INFO [05-12|13:42:13.083] [HookPenalty] get previous penalty node and add into comeback list addr=xdcDa133dA5981bf90E51c35E9Dfe5B9f604d65cE47
INFO [05-12|13:42:13.083] [HookPenalty] get previous penalty node and add into comeback list addr=xdce60986D35497291dde76c066Df27D56F153cBF06
INFO [05-12|13:42:13.083] [HookPenalty] get previous penalty node and add into comeback list addr=xdce65F06590eE4ED6D814309e5fA014B642b9272Bd
panic: runtime error: invalid memory address or nil pointer dereference
[signal SIGSEGV: segmentation violation code=0x1 addr=0x20 pc=0x65d6a0]

goroutine 739 [running]:
github.com/XinFinOrg/XDPoSChain/core/types.(*Block).Transactions(0xb34b3aa92a49e74e?)
    /builder/core/types/block.go:341
github.com/XinFinOrg/XDPoSChain/eth.New.AttachConsensusV2Hooks.func6({0x182ea88, 0xc000212bd0}, 0xc009a60dc0, {0x91, 0x8f, 0xba, 0x1b, 0xbb, 0x65, 0x69, ...}, ...)
    /builder/eth/hooks/engine_v2_hooks.go:126 +0xf77
github.com/XinFinOrg/XDPoSChain/consensus/XDPoS/engines/engine_v2.(*XDPoS_v2).calcMasternodes(0xc0001bc420, {0x182ea88, 0xc000212bd0}, 0xc009a60dc0, {0x86, 0x4a, 0xd0, 0xa4, 0x68, 0x3e, ...}, ...)
    /builder/consensus/XDPoS/engines/engine_v2/engine.go:1117 +0x188
github.com/XinFinOrg/XDPoSChain/consensus/XDPoS/engines/engine_v2.(*XDPoS_v2).verifyHeader(0xc0001bc420, {0x182ea88, 0xc000212bd0}, 0xc009a70288, {0xc001fa7808, 0x0, 0xa?}, 0x0)
    /builder/consensus/XDPoS/engines/engine_v2/verifyHeader.go:135 +0xd97
github.com/XinFinOrg/XDPoSChain/consensus/XDPoS/engines/engine_v2.(*XDPoS_v2).VerifyHeaders.func1()
    /builder/consensus/XDPoS/engines/engine_v2/engine.go:585 +0x136
created by github.com/XinFinOrg/XDPoSChain/consensus/XDPoS/engines/engine_v2.(*XDPoS_v2).VerifyHeaders in goroutine 619
    /builder/consensus/XDPoS/engines/engine_v2/engine.go:583 +0x105