drm/ttm: Avoid NULL pointer deref for evicted BOs

{
                    "product": "Linux",
                    "vendor": "Linux",
                    "defaultStatus": "unaffected",
                    "repo": "https://git.kernel.org/pub/scm/linux/kernel/git/stable/linux.git",
                    "programFiles": [
                        "drivers/gpu/drm/ttm/ttm_bo_vm.c"
                    ],
                    "versions": [
                        {
                            "version": "09ac4fcb3f255e9225967c75f5893325c116cdbe",
                            "lessThan": "47a85604a761005d255ae38115ee630cc6931756",
                            "status": "affected",
                            "versionType": "git"
                        },
                        {
                            "version": "09ac4fcb3f255e9225967c75f5893325c116cdbe",
                            "lessThan": "4b9944493c6d92d7b29cfd83aaf3deb842b8da79",
                            "status": "affected",
                            "versionType": "git"
                        },
                        {
                            "version": "09ac4fcb3f255e9225967c75f5893325c116cdbe",
                            "lessThan": "3d004f7341d4898889801ebb2ef61ffca610dd6f",
                            "status": "affected",
                            "versionType": "git"
                        },
                        {
                            "version": "09ac4fcb3f255e9225967c75f5893325c116cdbe",
                            "lessThan": "5a81095d3e1b521ac7cfe3b14d5f149bace3d6e0",
                            "status": "affected",
                            "versionType": "git"
                        },
                        {
                            "version": "09ac4fcb3f255e9225967c75f5893325c116cdbe",
                            "lessThan": "b94182b3d7228aec18d069cba56d5982e9bfe1b1",
                            "status": "affected",
                            "versionType": "git"
                        },
                        {
                            "version": "09ac4fcb3f255e9225967c75f5893325c116cdbe",
                            "lessThan": "491adc6a0f9903c32b05f284df1148de39e8e644",
                            "status": "affected",
                            "versionType": "git"
                        }
                    ]
                }

{
                    "product": "Linux",
                    "vendor": "Linux",
                    "defaultStatus": "affected",
                    "repo": "https://git.kernel.org/pub/scm/linux/kernel/git/stable/linux.git",
                    "programFiles": [
                        "drivers/gpu/drm/ttm/ttm_bo_vm.c"
                    ],
                    "versions": [
                        {
                            "version": "4.14",
                            "status": "affected"
                        },
                        {
                            "version": "0",
                            "lessThan": "4.14",
                            "status": "unaffected",
                            "versionType": "semver"
                        },
                        {
                            "version": "5.15.198",
                            "lessThanOrEqual": "5.15.*",
                            "status": "unaffected",
                            "versionType": "semver"
                        },
                        {
                            "version": "6.1.160",
                            "lessThanOrEqual": "6.1.*",
                            "status": "unaffected",
                            "versionType": "semver"
                        },
                        {
                            "version": "6.6.120",
                            "lessThanOrEqual": "6.6.*",
                            "status": "unaffected",
                            "versionType": "semver"
                        },
                        {
                            "version": "6.12.64",
                            "lessThanOrEqual": "6.12.*",
                            "status": "unaffected",
                            "versionType": "semver"
                        },
                        {
                            "version": "6.18.4",
                            "lessThanOrEqual": "6.18.*",
                            "status": "unaffected",
                            "versionType": "semver"
                        },
                        {
                            "version": "6.19",
                            "lessThanOrEqual": "*",
                            "status": "unaffected",
                            "versionType": "original_commit_for_fix"
                        }
                    ]
                }