media: mediatek: vcodec: Only free buffer VA that is not NULL

{
                    "product": "Linux",
                    "vendor": "Linux",
                    "defaultStatus": "unaffected",
                    "repo": "https://git.kernel.org/pub/scm/linux/kernel/git/stable/linux.git",
                    "programFiles": [
                        "drivers/media/platform/mediatek/vcodec/decoder/vdec/vdec_av1_req_lat_if.c",
                        "drivers/media/platform/mediatek/vcodec/encoder/venc/venc_h264_if.c"
                    ],
                    "versions": [
                        {
                            "version": "590577a4e5257ac3ed72999a94666ad6ba8f24bc",
                            "lessThan": "5c217253c76c94f76d1df31d0bbdcb88dc07be91",
                            "status": "affected",
                            "versionType": "git"
                        },
                        {
                            "version": "590577a4e5257ac3ed72999a94666ad6ba8f24bc",
                            "lessThan": "303d01082edaf817ee2df53a40dca9da637a2c04",
                            "status": "affected",
                            "versionType": "git"
                        },
                        {
                            "version": "590577a4e5257ac3ed72999a94666ad6ba8f24bc",
                            "lessThan": "eb005c801ec70ff4307727bd3bd6e8280169ef32",
                            "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/media/platform/mediatek/vcodec/decoder/vdec/vdec_av1_req_lat_if.c",
                        "drivers/media/platform/mediatek/vcodec/encoder/venc/venc_h264_if.c"
                    ],
                    "versions": [
                        {
                            "version": "4.10",
                            "status": "affected"
                        },
                        {
                            "version": "0",
                            "lessThan": "4.10",
                            "status": "unaffected",
                            "versionType": "semver"
                        },
                        {
                            "version": "6.6.39",
                            "lessThanOrEqual": "6.6.*",
                            "status": "unaffected",
                            "versionType": "semver"
                        },
                        {
                            "version": "6.9.9",
                            "lessThanOrEqual": "6.9.*",
                            "status": "unaffected",
                            "versionType": "semver"
                        },
                        {
                            "version": "6.10",
                            "lessThanOrEqual": "*",
                            "status": "unaffected",
                            "versionType": "original_commit_for_fix"
                        }
                    ]
                }