netfilter: flowtable: initialise extack before use

{
                    "product": "Linux",
                    "vendor": "Linux",
                    "defaultStatus": "unaffected",
                    "repo": "https://git.kernel.org/pub/scm/linux/kernel/git/stable/linux.git",
                    "programFiles": [
                        "net/netfilter/nf_flow_table_offload.c"
                    ],
                    "versions": [
                        {
                            "version": "c29f74e0df7a02b8303bcdce93a7c0132d62577a",
                            "lessThan": "e5ceff2196dc633c995afb080f6f44a72cff6e1d",
                            "status": "affected",
                            "versionType": "git"
                        },
                        {
                            "version": "c29f74e0df7a02b8303bcdce93a7c0132d62577a",
                            "lessThan": "356beb911b63a8cff34cb57f755c2a2d2ee9dec7",
                            "status": "affected",
                            "versionType": "git"
                        },
                        {
                            "version": "c29f74e0df7a02b8303bcdce93a7c0132d62577a",
                            "lessThan": "7eafeec6be68ebd6140a830ce9ae68ad5b67ec78",
                            "status": "affected",
                            "versionType": "git"
                        },
                        {
                            "version": "c29f74e0df7a02b8303bcdce93a7c0132d62577a",
                            "lessThan": "c7b760499f7791352b49b11667ed04b23d7f5b0f",
                            "status": "affected",
                            "versionType": "git"
                        },
                        {
                            "version": "c29f74e0df7a02b8303bcdce93a7c0132d62577a",
                            "lessThan": "119be227bc04f5035efa64cb823b8a5ca5e2d1c1",
                            "status": "affected",
                            "versionType": "git"
                        },
                        {
                            "version": "c29f74e0df7a02b8303bcdce93a7c0132d62577a",
                            "lessThan": "e9767137308daf906496613fd879808a07f006a2",
                            "status": "affected",
                            "versionType": "git"
                        }
                    ]
                }

{
                    "product": "Linux",
                    "vendor": "Linux",
                    "defaultStatus": "affected",
                    "repo": "https://git.kernel.org/pub/scm/linux/kernel/git/stable/linux.git",
                    "programFiles": [
                        "net/netfilter/nf_flow_table_offload.c"
                    ],
                    "versions": [
                        {
                            "version": "5.5",
                            "status": "affected"
                        },
                        {
                            "version": "0",
                            "lessThan": "5.5",
                            "status": "unaffected",
                            "versionType": "semver"
                        },
                        {
                            "version": "5.10.225",
                            "lessThanOrEqual": "5.10.*",
                            "status": "unaffected",
                            "versionType": "semver"
                        },
                        {
                            "version": "5.15.166",
                            "lessThanOrEqual": "5.15.*",
                            "status": "unaffected",
                            "versionType": "semver"
                        },
                        {
                            "version": "6.1.107",
                            "lessThanOrEqual": "6.1.*",
                            "status": "unaffected",
                            "versionType": "semver"
                        },
                        {
                            "version": "6.6.48",
                            "lessThanOrEqual": "6.6.*",
                            "status": "unaffected",
                            "versionType": "semver"
                        },
                        {
                            "version": "6.10.7",
                            "lessThanOrEqual": "6.10.*",
                            "status": "unaffected",
                            "versionType": "semver"
                        },
                        {
                            "version": "6.11",
                            "lessThanOrEqual": "*",
                            "status": "unaffected",
                            "versionType": "original_commit_for_fix"
                        }
                    ]
                }