Catch exception for non supported image type by PixbufLoader

(transplanted from 09e92c3e15d403ad128aaf29c7c94469408f88a9)

tryton/gui/window/view_form/view/form_gtk/image.py

@@ -154,8 +154,8 @@ class Image(WidgetInterface):
 
         pixbuf = None
         for ftype in ('jpeg', 'gif', 'png', 'bmp'):
-            loader = gtk.gdk.PixbufLoader(ftype)
             try:
+                loader = gtk.gdk.PixbufLoader(ftype)
                 loader.write(data, len(data))
             except:
                 continue