CLONE - Indexer panics if an index is dropped while index mutation is ongoing

panic: metadata2/ixTEST/Backstore#600729674437986272:0 : fatal: Invalid page data type 101 on offset 23788165853

goroutine 411 [running]:
panic(0xe223a0, 0xc5476ebf40)
/home/couchbase/.cbdepscache/exploded/x86_64/go-1.7.6/go/src/runtime/panic.go:500 +0x1a1 fp=0xc46fa8ed00 sp=0xc46fa8ec70
github.com/couchbase/plasma.(*Plasma).fatalPanic(0xc423bfe400, 0xc43ea4b680, 0x30)
goproj/src/github.com/couchbase/plasma/plasma.go:1787 +0x310 fp=0xc46fa8f190 sp=0xc46fa8ed00
github.com/couchbase/plasma.(*Plasma).fetchPageSegmentFromLSS(0xc423bfe400, 0x589e29add, 0xc423da3860, 0xc656ee7540, 0xc423dc23c0, 0xc4e8d41400, 0x1, 0x589e29add, 0x0, 0x0)
goproj/src/github.com/couchbase/plasma/plasma.go:1761 +0x5f2 fp=0xc46fa8f268 sp=0xc46fa8f190
github.com/couchbase/plasma.(*Plasma).(github.com/couchbase/plasma.fetchPageSegmentFromLSS)-fm(0x589e29add, 0xc423da3860, 0xc656ee7540, 0xc423dc23c0, 0x3b8b6177123, 0x0, 0x589e29add, 0x0, 0x0)
goproj/src/github.com/couchbase/plasma/plasma.go:1160 +0x56 fp=0xc46fa8f2c8 sp=0xc46fa8f268
github.com/couchbase/plasma.(*pageWalker).readPageSegment(0xc57b174240)
goproj/src/github.com/couchbase/plasma/page_walker.go:159 +0x99 fp=0xc46fa8f3a0 sp=0xc46fa8f2c8
github.com/couchbase/plasma.(*pageWalker).Next(0xc57b174240)
goproj/src/github.com/couchbase/plasma/page_walker.go:148 +0x61 fp=0xc46fa8f3c0 sp=0xc46fa8f3a0
github.com/couchbase/plasma.(*page).Lookup(0xc57b172cc0, 0x7fce56f57000, 0x0)
goproj/src/github.com/couchbase/plasma/page.go:509 +0x2ea fp=0xc46fa8f600 sp=0xc46fa8f3c0
github.com/couchbase/plasma.(*Writer).Lookup(0xc423d55660, 0x7fce56f57000, 0x24, 0x24, 0x0)
goproj/src/github.com/couchbase/plasma/plasma.go:1710 +0xcf fp=0xc46fa8f688 sp=0xc46fa8f600
github.com/couchbase/plasma.(*Writer).LookupKV(0xc423d55660, 0xc49f1b0c60, 0x24, 0x24, 0xc414ed50de, 0x18858a0, 0xca0b9, 0x0, 0x0)
goproj/src/github.com/couchbase/plasma/mvcc.go:332 +0x109 fp=0xc46fa8f720 sp=0xc46fa8f688
github.com/couchbase/indexing/secondary/indexer.(*plasmaSlice).insertSecArrayIndex(0xc4200f4000, 0xc51d9c4000, 0xa8cc, 0xc000, 0xc49f1b0c60, 0x24, 0x24, 0x6, 0xc46fa8fc00, 0xc510497f20, ...)
goproj/src/github.com/couchbase/indexing/secondary/indexer/plasma_slice.go:621 +0x245f fp=0xc46fa8fc58 sp=0xc46fa8f720
github.com/couchbase/indexing/secondary/indexer.(*plasmaSlice).insert(0xc4200f4000, 0xc51d9c4000, 0xa8cc, 0xc000, 0xc49f1b0c60, 0x24, 0x24, 0x6, 0x7fcea8cf7400, 0xc510497f20, ...)
goproj/src/github.com/couchbase/indexing/secondary/indexer/plasma_slice.go:528 +0xc7 fp=0xc46fa8fcc8 sp=0xc46fa8fc58
github.com/couchbase/indexing/secondary/indexer.(*plasmaSlice).handleCommandsWorker(0xc4200f4000, 0x6)
goproj/src/github.com/couchbase/indexing/secondary/indexer/plasma_slice.go:481 +0x277 fp=0xc46fa8ff40 sp=0xc46fa8fcc8
runtime.goexit()
/home/couchbase/.cbdepscache/exploded/x86_64/go-1.7.6/go/src/runtime/asm_amd64.s:2086 +0x1 fp=0xc46fa8ff48 sp=0xc46fa8ff40
created by github.com/couchbase/indexing/secondary/indexer.(*plasmaSlice).initWriters
goproj/src/github.com/couchbase/indexing/secondary/indexer/plasma_slice.go:2149 +0x3b3

Supportal link: https://supportal.couchbase.com/snapshot/3518d5c792ee95d2c475a10b602f4ea4::2