Handle case where user has moved away since confirming Sphere

[dgor82]

Scenario:

1. User has liveLocation sharing on
2. User starts new submission, and near sphere is recoginsed and confirmation dialogue shown
3. User moves away from the sphere
4. User now confirms the suggested sphere, even though not near anymore

In NewIssueSphereConfirmation.GetPromptAsync(), add e.g.

    if (nearSphere.IsNone)
    {
    }

It's an edge case. I think should simply reroute to SphereSelection state/prompt. But some handling is needed in order to avoid a crash from nearSphere.GetValueOrThrow().Name later in the same method