This is likely to be overkill but seems to fix a regression introduced
by e73a9c1b

: Persistent model indices owned by the selection
model of the watch view lose their model pointer and consequently
cause error messages to be emitted and potentially cause crashes.

Change-Id: I3334ca25bb5e2facf51d03c50647f95f55786498
Reviewed-by: David Schulz <david.schulz@theqtcompany.com>