[FIX] web: allow default behavior for unmanaged keyboard navigation

Reproduce the issue:
- open the manual reconciliation (it is a client action)
- add a reconciliation (using the + sign)
- expand it (using the > sign)
- put the focus on the first field and hit TAB
--> you would expect that the focus moves to the second field
--> what happens is: the focus stays on the first field

Before this fix, when in a client action (or any place that contains
fields) that contains fields, the keyboard navigation did not occur
correctly because the default behavior of the TAB key was prevented.

After this fix, if the navigation_move event was not stopped, we allow
the default behavior of the TAB key.