[Vala] Type initialization error in gnome3(fallback) applet experiment.

[Tal Hadad <tal_hd hotmail com>]

I try to support my project(MPRIS Applet) into GNOME3 fallback mode, as an in process applet.

But I run into a trouble- I got an error while loading this applet.
For debug it I typed in one terminal:
startx gnome-session-fallback -- :1

Inside the gnome session I restarted gnome-panel(when my applet is in the panel with failure), by:
gnome-panel --replace

Then, I get this error log:

...
...

(gnome-panel:24097):
 Gtk-WARNING **: Theme parsing error: gtk-widgets.css:858:36: Failed to 
import: Error opening file: No such file or directory

(gnome-panel:24097):
 GLib-GObject-WARNING **: 
/tmp/buildd/glib2.0-2.30.2/./gobject/gsignal.c:2295: signal 
`size_request' is invalid for instance `0x2046da0'

** (gnome-panel:24097): WARNING **: Failed to get pixmap 14680140, 923, 0

** (gnome-panel:24097): WARNING **: Failed to get pixmap 14680140, 78, 0

** (gnome-panel:24097): WARNING **: Failed to get pixmap 14680140, 0, 0

(gnome-panel:24097): Gtk-CRITICAL **: gtk_drag_set_icon_gicon: assertion `icon != NULL' failed

(gnome-panel:24097): GLib-GObject-CRITICAL **: g_object_unref: assertion `G_IS_OBJECT (object)' failed

(gnome-panel:24097):
 GLib-GObject-WARNING **: specified class size for type `MainApplet' is 
smaller than the parent type's `PanelApplet' class size

(gnome-panel:24097): GLib-CRITICAL **: g_once_init_leave: assertion `initialization_value != 0' failed
**
ERROR:panel-applet.c:2535:_panel_applet_factory_main_internal: assertion failed: (g_type_is_a (applet_type, 
PANEL_TYPE_APPLET))
Aborted
$ 

The "..." is GTK warning about the theme, very long and isn't related.
It is happening because of invalid type initialization, somehow class is smaller then parent.
At
 first, I thought it is invaild/outdated headers problem. But in my 
Debian machine, the -dev package is in the same version of the library 
package
of libpanel-applet-4.0(3.2.1-2+b1).
I even tried to add fields and virtual methods as a desperate solution, but still haven't helped.

Therefore I made&uploaded a little example of this problem packed into a autoconf tarball so you can test it 
by yourself:

http://www.mediafire.com/?g9xsaaybpn386ej

About the source files:
src/register.c: A convenient GMoudle register file into in process applet, since Vala doesn't support this 
kind of macros.
src/main_applet.vala: The applet it self.

Here is a nice example how it shell look in C, the Fish applet example:
http://gnome-panel.sourcearchive.com/documentation/3.0.2-1/fish_8c_source.html

Can you please see why the type fail to be initialized?

Thanks
Tal