by using G_TYPE_NONE (== 1), we can pass this in the log handler
to point out the fact that we expected something but it's null
As a bonus, a null object always gets printed in red because that's
the first color in object_colors
Add the 'const' attribute to let the compiler know that it doesn't
need to call it multiple times for the same debug level argument,
since the enabled log levels cannot change at runtime.
This extends GLib's logging system, so it is compatible with
g_debug() and friends, but it uses a better logging format and
supports filtering debug domains with wildcards, like in gst.
