[Device Notifier] Avoid accessing attributes of stale UDIs
Summary:
When a Solid device is removed (e.g. a CD is ejected) the notifier tries
to read the attributes although the Source for the UDI has just vanished.
Fixes several QML error messages, i.e. "TypeError: Cannot read property
'...' of undefined" and "Unable to assign [undefined] to QString".
Apparently these errors also have the effect of items showing outdated
state, i.e. optical media still being shown after ejecting it.
CCBUG: 394348
Test Plan:
- insert optical medium
- eject
Without the changes, the item was stuck
Now, the item is removed as soon as the medium is ejected
Also, no more errors are logged for the devicenotifier
Reviewers: Frameworks, broulik
Reviewed By: broulik
Subscribers: ngraham, plasma-devel
Tags: Plasma
Differential Revision: https://phabricator.kde.org/D15687