Fix spam from pointcloud task when there is no EAP

[heuristicus]

PR #64 included a pointcloud task to get clouds from the EAP, but if the EAP doesn't exist then this would cause some spam like

Update tasks failed with error: 'NoneType' object has no attribute 'get_point_cloud_async'
Update tasks failed with error: 'NoneType' object has no attribute 'get_point_cloud_async'
Update tasks failed with error: 'NoneType' object has no attribute 'get_point_cloud_async'
Update tasks failed with error: 'NoneType' object has no attribute 'get_point_cloud_async'
Update tasks failed with error: 'NoneType' object has no attribute 'get_point_cloud_async'

on every task update. This PR fixes that by checking if the point cloud client isn't none, and only creating the task and adding it to the list if it exists.

Also makes the warning on adding an image task more obvious about what task already existed in the list.

[jeremysee2]

That looks good to me, I saw that logging too when my EAP was turned off.