[Bug] source-added signal, user data corrupted

[Iago Toral <itoral igalia com>]

Hey,

since we don't have the Bugzilla ready yet I'll post it here, maybe someone 
has time to look into this :)

When a new media source is registered the plugin registry emits a signal named 
source-added, you can see this for example in grilo-test-ui. When you add g_signal_connect 
to connect to this signal you're allowed to pass a user_data parameter for the 
signal handler (we pass NULL in grilo-test-ui). I have checked that this user_data, 
when received on the signal handler is corrupted (just pass a string instead 
of NULL in grilo-test-ui). I managed to reproduce this with grilo-test-ui and 
other examples so I guess there is something wrong in the plugin registry code 
somewhere. I did not spot anything at first sight and a quick check with valgrind 
(maybe someone could give this a try again) did not show any issues.

Iago