Precise that indexUid can be null

Author: gmourier

text/0060-tasks-api.md

@@ -58,7 +58,7 @@ The motivation is to stabilize the current `update` resource to a version that c
 | field   | type    | description                     |
 |---------|---------|---------------------------------|
 | uid      | integer | Unique sequential identifier           |
-| indexUid | string | Unique index identifier. This field is `null` when the task type is `dumpCreation`. |
+| indexUid | string or null  | Unique index identifier. This field is `null` when the task type is `dumpCreation`. |
 | batchUid | integer | Identify in which batch a task has been grouped by auto-batching. It corresponds to the first task uid grouped within a batch. See [auto-batching specification](0096-auto-batching.md) |
 | status  | string  | Status of the task. Possible values are `enqueued`, `processing`, `succeeded`, `failed`                                |
 | type    | string  | Type of the task. Possible values are `indexCreation`, `indexUpdate`, `indexDeletion`, `documentAddition`, `documentPartial`, `documentDeletion`, `settingsUpdate`, `clearAll`, `dumpCreation` |