Crash in the scopes middleware when executing search immediately after a scope was uninstalled

[Paweł Stołowski]

Unity8 crashes when uninstalling youtube scope via Ubuntu Store. This only happens with latest unity-scope-shell (trunk).
One of the latest changes to the shell plugin re-executes search in Ubuntu store when packages are installed or removed, and this triggers this bug, but only when removing scopes.

Steps to reproduce:

1. Make sure youtube scope is installed.
2. Go to Ubuntu Store -> Music & Audio department
3. Scroll to bottom, find youtube scope in the Store results. Click it to get the preview.
4. In the preview, click Uninstall and confirm.
5. When uninstall completes, click the "back" arrow at the top (that should take you back to search results).

The following error appears in unity8-dash.log:

unity::scopes::MiddlewareException: Cannot invoke operations while middleware is stopped
unexpected exception in add_reply_object(): basic_string::_S_create
unity8-dash: /build/buildd/unity-scopes-api-0.6.6+14.10.20140916/src/scopes/internal/AbstractObject.cpp:58: void unity::scopes::internal::AbstractObject::disconnect(): Assertion `disconnect_func_' failed.

I wasn't able to get a backtrace of this crash - gdb either gives me 3 corrupted frames, or hangs.

It only crashes when uninstalling scope (doesn't crash for apps). There may be a problem with a search request executed at a time registry changes happen.

[Launchpad Janitor (janitor)]

This bug was fixed in the package unity-scopes-shell - 0.5.4+14.10.20141002.1-0ubuntu1

---------------
unity-scopes-shell (0.5.4+14.10.20141002.1-0ubuntu1) utopic; urgency=low

  [ Marcus Tomlinson ]
  * Use refreshScopeMetadata() rather than populateScopes() when
    invalidating results (populateScopes() is intended for use only on
    start-up) (LP: #1376755)
 -- Ubuntu daily release <email address hidden> Thu, 02 Oct 2014 19:20:45 +0000