nfs/blocklayout: Don't attempt unregister for invalid block device

{
                    "product": "Linux",
                    "vendor": "Linux",
                    "defaultStatus": "unaffected",
                    "repo": "https://git.kernel.org/pub/scm/linux/kernel/git/stable/linux.git",
                    "programFiles": [
                        "fs/nfs/blocklayout/dev.c"
                    ],
                    "versions": [
                        {
                            "version": "d869da91cccb90320e101a2758f1e2b3803ade5c",
                            "lessThan": "3402704a424f34bbcca7f4a4503859357f422217",
                            "status": "affected",
                            "versionType": "git"
                        },
                        {
                            "version": "d869da91cccb90320e101a2758f1e2b3803ade5c",
                            "lessThan": "faa4bacfaeed827a4ca8cb8529a3ce65a9e8ef46",
                            "status": "affected",
                            "versionType": "git"
                        },
                        {
                            "version": "d869da91cccb90320e101a2758f1e2b3803ade5c",
                            "lessThan": "3a4ce14d9a6b868e0787e4582420b721c04ee41e",
                            "status": "affected",
                            "versionType": "git"
                        }
                    ]
                }

{
                    "product": "Linux",
                    "vendor": "Linux",
                    "defaultStatus": "affected",
                    "repo": "https://git.kernel.org/pub/scm/linux/kernel/git/stable/linux.git",
                    "programFiles": [
                        "fs/nfs/blocklayout/dev.c"
                    ],
                    "versions": [
                        {
                            "version": "6.11",
                            "status": "affected"
                        },
                        {
                            "version": "0",
                            "lessThan": "6.11",
                            "status": "unaffected",
                            "versionType": "semver"
                        },
                        {
                            "version": "6.11.11",
                            "lessThanOrEqual": "6.11.*",
                            "status": "unaffected",
                            "versionType": "semver"
                        },
                        {
                            "version": "6.12.2",
                            "lessThanOrEqual": "6.12.*",
                            "status": "unaffected",
                            "versionType": "semver"
                        },
                        {
                            "version": "6.13",
                            "lessThanOrEqual": "*",
                            "status": "unaffected",
                            "versionType": "original_commit_for_fix"
                        }
                    ]
                }