dlm: fix possible lkb_resource null dereference

{
                    "product": "Linux",
                    "vendor": "Linux",
                    "defaultStatus": "unaffected",
                    "repo": "https://git.kernel.org/pub/scm/linux/kernel/git/stable/linux.git",
                    "programFiles": [
                        "fs/dlm/lock.c"
                    ],
                    "versions": [
                        {
                            "version": "43279e5376017c40b4be9af5bc79cbb4ef6f53d7",
                            "lessThan": "e1ffea6bec96d4349dbfcc42ad3e436259f64243",
                            "status": "affected",
                            "versionType": "git"
                        },
                        {
                            "version": "43279e5376017c40b4be9af5bc79cbb4ef6f53d7",
                            "lessThan": "8d55ce46dd543c6965970ce70c22c3076dd35b1e",
                            "status": "affected",
                            "versionType": "git"
                        },
                        {
                            "version": "43279e5376017c40b4be9af5bc79cbb4ef6f53d7",
                            "lessThan": "6fbdc3980b70e9c1c86eccea7d5ee68108008fa7",
                            "status": "affected",
                            "versionType": "git"
                        },
                        {
                            "version": "43279e5376017c40b4be9af5bc79cbb4ef6f53d7",
                            "lessThan": "2db11504ef82a60c1a2063ba7431a5cd013ecfcb",
                            "status": "affected",
                            "versionType": "git"
                        },
                        {
                            "version": "43279e5376017c40b4be9af5bc79cbb4ef6f53d7",
                            "lessThan": "b98333c67daf887c724cd692e88e2db9418c0861",
                            "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/dlm/lock.c"
                    ],
                    "versions": [
                        {
                            "version": "2.6.30",
                            "status": "affected"
                        },
                        {
                            "version": "0",
                            "lessThan": "2.6.30",
                            "status": "unaffected",
                            "versionType": "semver"
                        },
                        {
                            "version": "5.15.209",
                            "lessThanOrEqual": "5.15.*",
                            "status": "unaffected",
                            "versionType": "semver"
                        },
                        {
                            "version": "6.1.167",
                            "lessThanOrEqual": "6.1.*",
                            "status": "unaffected",
                            "versionType": "semver"
                        },
                        {
                            "version": "6.6.66",
                            "lessThanOrEqual": "6.6.*",
                            "status": "unaffected",
                            "versionType": "semver"
                        },
                        {
                            "version": "6.12.5",
                            "lessThanOrEqual": "6.12.*",
                            "status": "unaffected",
                            "versionType": "semver"
                        },
                        {
                            "version": "6.13",
                            "lessThanOrEqual": "*",
                            "status": "unaffected",
                            "versionType": "original_commit_for_fix"
                        }
                    ]
                }