[FIX] Avoid getting label by negative index

[TropicalPenguin]

I've not diagnosed rhe root cause; hopefully this points to it though.

With a query, "MATCH (s)-[r:incs]-(l:EC) WHERE ID(s)=3 RETURN r,l", which should be retrieving:

127.0.0.1:6379> GRAPH.QUERY G:1 "MATCH (s)-[r:incs]-(l:EC) WHERE ID(s)=3 RETURN r,l" 1) 1) "r" 2) "l" 2) 1) 1) 1) 1) "id" 2) (integer) 4 2) 1) "type" 2) "incs" 3) 1) "src_node" 2) (integer) 3 4) 1) "dest_node" 2) (integer) 6 5) 1) "properties" 2) 1) 1) "Net" 2) "c4peu14uj9oqljf5dkn0" 2) 1) 1) "id" 2) (integer) 6 2) 1) "labels" 2) 1) "EC" 3) 1) "properties" 2) 1) 1) "IDs" 2) "[0, 4, 3]"

I instead get:

runtime error: index out of range [-2] goroutine 210 [running]: net/http.(conn).serve.func1(0xc0002fc140) /usr/lib/go-1.16/src/net/http/server.go:1824 +0x153 panic(0x9842e0, 0xc0014c04b0) /usr/lib/go-1.16/src/runtime/panic.go:971 +0x499 github.com/redislabs/redisgraph-go.(Graph).getLabel(0xc0018faea0, 0xfffffffffffffffe, 0x0, 0x0) ~/Dev/go/pkg/mod/github.com/redislabs/redisgraph-go@v2.0.2+incompatible/graph.go:141 +0x152 github.com/redislabs/redisgraph-go.(QueryResult).parseNode(0xc0017e5e00, 0x908040, 0xc00081adf8, 0x0) ~/Dev/go/pkg/mod/github.com/redislabs/redisgraph-go@v2.0.2+incompatible/query_result.go:179 +0x219 github.com/redislabs/redisgraph-go.(QueryResult).parseScalar(0xc0017e5e00, 0xc001461cc0, 0x2, 0x2, 0xc001461cc0, 0x2) ~/Dev/go/pkg/mod/github.com/redislabs/redisgraph-go@v2.0.2+incompatible/query_result.go:257 +0x2b7 github.com/redislabs/redisgraph-go.(QueryResult).parseRecords(0xc0017e5e00, 0xc0017d2d80, 0x3, 0x3) ~/Dev/go/pkg/mod/github.com/redislabs/redisgraph-go@v2.0.2+incompatible/query_result.go:139 +0x434 github.com/redislabs/redisgraph-go.(QueryResult).parseResults(0xc0017e5e00, 0xc0017d2d80, 0x3, 0x3) ~/Dev/go/pkg/mod/github.com/redislabs/redisgraph-go@v2.0.2+incompatible/query_result.go:99 +0x77 github.com/redislabs/redisgraph-go.QueryResultNew(0xc0018faea0, 0x908040, 0xc00081aea0, 0xc0017d2d20, 0x3, 0x3) ~/Dev/go/pkg/mod/github.com/redislabs/redisgraph-go@v2.0.2+incompatible/query_result.go:85 +0x1da github.com/redislabs/redisgraph-go.(*Graph).Query(0xc0018faea0, 0xc0013cba80, 0x32, 0x7effa2628108, 0x40, 0xc0013cba80) ~/Dev/go/pkg/mod/github.com/redislabs/redisgraph-go@v2.0.2+incompatible/graph.go:108 +0x171