Can not aggregate query when there are some null values in records!!!(version 0.8.2)

Query: [select median(instantaneous_ops_per_sec) as instantaneous_ops_per_sec,median(connected_clients) as connected_clients,median(used_memory) as used_memory,me
dian(expired_keys) as expired_keys,median(net_io_in_per_sec) as net_io_in_per_sec,median(net_io_out_per_sec) as net_io_out_per_sec from /^instance.*/ group by tim
e(2m)]
Error: interface conversion: interface is nil, not *engine.PercentileAggregatorState. Stacktrace: goroutine 5449 [running]:
github.com/influxdb/influxdb/common.RecoverFunc(0xc2091683e8, 0x7, 0xc20adfa840, 0x141, 0x7fe708189ef0)
    /root/gocodez/src/github.com/influxdb/influxdb/common/recover.go:14 +0xb7
runtime.panic(0xbd13c0, 0xc2098c4e00)
    /root/.gvm/gos/go1.3.1/src/pkg/runtime/panic.c:248 +0x18d
github.com/influxdb/influxdb/engine.(*PercentileAggregator).CalculateSummaries(0xc20d6b1bc0, 0x0, 0x0)
    /root/gocodez/src/github.com/influxdb/influxdb/engine/aggregator.go:889 +0x3a
github.com/influxdb/influxdb/engine.func·010(0x0, 0x0, 0x0, 0xc20a7deb00, 0x0, 0x0)
    /root/gocodez/src/github.com/influxdb/influxdb/engine/engine.go:511 +0x10b
github.com/influxdb/influxdb/engine.(*Trie).TraverseLevel(0xc2098d5860, 0xffffffffffffffff, 0x7fe7081899a8, 0x0, 0x0)
    /root/gocodez/src/github.com/influxdb/influxdb/engine/trie.go:55 +0x5d
github.com/influxdb/influxdb/engine.(*Trie).Traverse(0xc2098d5860, 0x7fe7081899a8, 0x0, 0x0)
    /root/gocodez/src/github.com/influxdb/influxdb/engine/trie.go:49 +0x4c
github.com/influxdb/infl

![record2](https://cloud.githubusercontent.com/assets/7158763/4268821/4a9e06da-3cb4-11e4-9284-e0c7680fe873.PNG)

![record](https://cloud.githubusercontent.com/assets/7158763/4268797/f27f9518-3cb3-11e4-9c46-33132b705bb8.PNG)