panic: runtime error: slice bounds out of range [:-1]

goroutine 1273 [running]:
github.com/quay/claircore/rhel/dockerfile.(*labelParser).Run(0xc000389410)
/go/pkg/mod/github.com/quay/claircore@v1.1.3/rhel/dockerfile/dockerfile.go:99 +0x916
github.com/quay/claircore/rhel/dockerfile.GetLabels({0xc0006c1338, 0x410e76}, {0xf8b420, 0xc0003fd1a0})
/go/pkg/mod/github.com/quay/claircore@v1.1.3/rhel/dockerfile/dockerfile.go:26 +0x91
github.com/quay/claircore/rhel.extractBuildNVR(
{0xfa6330, 0xc00059ac00}, {0xc00093fdc0, 0x37}, 0x0)
/go/pkg/mod/github.com/quay/claircore@v1.1.3/rhel/repositoryscanner.go:315 +0x55
github.com/quay/claircore/rhel.(*RepositoryScanner).getCPEsUsingContainerAPI(0xc000ab5080, {0xfa6330, 0xc00059ac00}, 0x3)
/go/pkg/mod/github.com/quay/claircore@v1.1.3/rhel/repositoryscanner.go:248 +0xd4
github.com/quay/claircore/rhel.(*RepositoryScanner).Scan(0xc000ab5080,
{0xfa6368, 0xc000388ed0}, 0xc000ab5020)
/go/pkg/mod/github.com/quay/claircore@v1.1.3/rhel/repositoryscanner.go:187 +0x767
github.com/quay/claircore/internal/indexer/layerscanner.(*result).Do(0xc0006c1e68, {0xfa6368, 0xc000388ed0}, {0x7f9f24065748, 0xc000ab5080}, 0xc000712230)
/go/pkg/mod/github.com/quay/claircore@v1.1.3/internal/indexer/layerscanner/layerscanner.go:241 +0x162
github.com/quay/claircore/internal/indexer/layerscanner.(*layerScanner).scanLayer(0xc000ab52c0, {0xfa62c0, 0xc0003a7e40}, 0xc000ab5020, {0x7f9f24065748, 0xc000ab5080})
/go/pkg/mod/github.com/quay/claircore@v1.1.3/internal/indexer/layerscanner/layerscanner.go:212 +0x89c
github.com/quay/claircore/internal/indexer/layerscanner.(*layerScanner).Scan.func1.1()
/go/pkg/mod/github.com/quay/claircore@v1.1.3/internal/indexer/layerscanner/layerscanner.go:173 +0x125
golang.org/x/sync/errgroup.(*Group).Go.func1()
/go/pkg/mod/golang.org/x/sync@v0.0.0-20210220032951-036812b2e83c/errgroup/errgroup.go:57 +0x67
created by golang.org/x/sync/errgroup.(*Group).Go
/go/pkg/mod/golang.org/x/sync@v0.0.0-20210220032951-036812b2e83c/errgroup/errgroup.go:54 +0x92