Please describe the problem:
Acquiring Data progress dialog never completes or disappears.  At about 95% progress, it stalls, writes the image to disk (not sure if it's complete) and starts again at 0% acquiring data.  

Steps to reproduce:
1. Open Flegita or launch from Acquire menu within Gimp.
2. Click Scan.



Actual results:
The 'Acquiring Progress' bar reaches maybe 95%, stalls, the image is written to disk, and the process is started again.  I'm not sure if the image is actually incomplete or not.  This repeats until I manually stop it.

Expected results:
The image to be scanned once and for the Acquiring Data progress to complete and disappear, maybe with an acknowledgement that the scanning process has completed.

Does this happen every time?
This occurs when I either launch flegita by itself or from within the Acquire menu the Gimp.

Other information:
I cannot select a DPI from the advanced tab, both the X and Y resolutions stay at 0.

Running from the console, I got the following output:

$ flegita --version
GNOME gnomescan 0.4.0.4

$ flegita
(gnomescan:5068): GnomeScan-DEBUG: Scanner MFC-420CN selected
(gnomescan:5068): GnomeScan-DEBUG: Area set to 0.000000×0.000000+107.949997+0.000000 (mm)

(gnomescan:5068): GdkPixbuf-CRITICAL **: gdk_pixbuf_get_height: assertion `pixbuf != NULL' failed

(gnomescan:5068): GdkPixbuf-CRITICAL **: gdk_pixbuf_get_width: assertion `pixbuf != NULL' failed
(gnomescan:5068): GnomeScan-DEBUG: Area set to 0.000000×0.000000+107.949997+0.000000 (mm)
(gnomescan:5068): GnomeScan-DEBUG: Area set to 0.000000×0.000000+107.949997+0.000000 (mm)

(gnomescan:5068): GdkPixbuf-CRITICAL **: gdk_pixbuf_get_height: assertion `pixbuf != NULL' failed

(gnomescan:5068): GdkPixbuf-CRITICAL **: gdk_pixbuf_get_width: assertion `pixbuf != NULL' failed

(gnomescan:5068): GdkPixbuf-CRITICAL **: gdk_pixbuf_get_height: assertion `pixbuf != NULL' failed

(gnomescan:5068): GdkPixbuf-CRITICAL **: gdk_pixbuf_get_width: assertion `pixbuf != NULL' failed
(gnomescan:5068): GnomeScan-DEBUG: 0 px @ 50.000000 dpi = 0.000000mm
(gnomescan:5068): GnomeScan-DEBUG: 0 px @ 50.000000 dpi = 0.000000mm
(gnomescan:5068): GnomeScan-DEBUG: 425 px @ 50.000000 dpi = 215.899995mm
(gnomescan:5068): GnomeScan-DEBUG: 700 px @ 50.000000 dpi = 355.599991mm
(gnomescan:5068): GnomeScan-DEBUG: Area set to 215.899995×355.599991+0.000000+0.000000 (mm)
(gnomescan:5068): GnomeScan-DEBUG: Area set to 215.899995×355.599991+-0.000000+0.000000 (mm)
(gnomescan:5068): GnomeScan-DEBUG: Area set to 215.899994×279.399994+0.000000+69.849999 (mm)
(gnomescan:5068): GnomeScan-DEBUG: Area set to 215.899994×279.399994+0.000000+0.000000 (mm)
(gnomescan:5068): GnomeScanUI-DEBUG: Will receive 11208303 bytes

(gnomescan:5068): GLib-GObject-WARNING **: instance of invalid non-instantiatable type `-g-type-private--GTypeFlags'

(gnomescan:5068): GLib-GObject-CRITICAL **: g_signal_emit_valist: assertion `G_TYPE_CHECK_INSTANCE (instance)' failed

(gnomescan:5068): GLib-GObject-WARNING **: instance of invalid non-instantiatable type `-g-type-private--GTypeFlags'

(gnomescan:5068): GLib-GObject-CRITICAL **: g_signal_handlers_destroy: assertion `G_TYPE_CHECK_INSTANCE (instance)' failed

(gnomescan:5068): GLib-GObject-WARNING **: instance of invalid non-instantiatable type `-g-type-private--GTypeFlags'

(gnomescan:5068): GLib-GObject-CRITICAL **: g_signal_handlers_destroy: assertion `G_TYPE_CHECK_INSTANCE (instance)' failed

(gnomescan:5068): GLib-GObject-CRITICAL **: g_object_unref: assertion `G_IS_OBJECT (object)' failed