TodoEntryV2's Get method returns tasks with linkUrl null

[#1]

TodoEntryV2 - GET Method's response payload has few tasks with linkUrl null. One such response payload below:

{
"__metadata": {
"uri": "https://apisalesdemo4.successfactors.com:443/odata/v2/TodoEntryV2(23951M)",
"type": "SFOData.TodoEntryV2"
},
"todoEntryId": "23951",
"lastModifiedDateTime": "/Date(1351396800000+0000)/",
"dueDate": null,
"todoEntryName": "Complete 360 Evaluation",
"categoryLabel": "Collect 360 Feedback",
"completedDateTime": null,
"mobileLinkUrl": null,
"subjectId": null,
"createdDate": "/Date(1351396800000+0000)/",
"linkUrl": null,
"formDataId": 7538,
"categoryId": "2",
"status": 2,
"userNav": {
"__deferred": {
"uri": "https://apisalesdemo4.successfactors.com:443/odata/v2/TodoEntryV2(23951M)/userNav"
}
},
"recruitingJobOfferNav": {
"__deferred": {
"uri": "https://apisalesdemo4.successfactors.com:443/odata/v2/TodoEntryV2(23951M)/recruitingJobOfferNav"
}
},
"formContentNav": {
"__deferred": {
"uri": "https://apisalesdemo4.successfactors.com:443/odata/v2/TodoEntryV2(23951M)/formContentNav"
}
},
"wfRequestNav": {
"__deferred": {
"uri": "https://apisalesdemo4.successfactors.com:443/odata/v2/TodoEntryV2(23951M)/wfRequestNav"
}
}
}

We plan to display this field to user. They can click on the link, login and complete the task in SF. Why is this field empty? What is the alternate link to display to user?