Fix crash when the relatedTo on a todo becomes empty
Fix crash when the relatedTo on a todo becomes empty

When a todo is moved to the inbox the relatedTo becomes empty
we need to remove the uid of the item from the parentMap.

sandsmark/zanshin,sandsmark/zanshin,kolab-groupware/zanshin,sandsmark/zanshin,kolab-groupware/zanshin,kolab-groupware/zanshin