\u0000 in reference data causes database error

[Daniel Robinson]

Submitting a transaction with reference data that contains the sequence \u0000 causes cored to enter an infinite loop printing the following error:

/Users/danielrobinson/Projects/go/src/chain/core/query/index.go:137 - chain/core/query.(*Indexer).insertAnnotatedTxs
/Users/danielrobinson/Projects/go/src/chain/core/query/index.go:69 - chain/core/query.(*Indexer).IndexTransactions
/Users/danielrobinson/Projects/go/src/chain/core/query/index.go:55 - chain/core/query.(*Indexer).IndexTransactions-fm
/Users/danielrobinson/Projects/go/src/chain/core/pin/pin.go:214 - chain/core/pin.(*pin).processBlock
/usr/local/Cellar/go/1.8/libexec/src/runtime/asm_amd64.s:2197 - runtime.goexit

[Jackson Owens]

Fixed in #1240.