[Qgis-user] Problem using Add Island

[Vito Meuli]

Hi all!
I'm trying to add an island to a MULTIPOLYGON geometry stored in a shapefile.

It seems that if I have the old geometry on screen, then I can add the island; 
if I pan far enough not to have the old geometry on screen anymore, then I 
cannot add the island!

A colleague of mine discovered something more: after that I have already added 
an island to the geometry (both drawed on the screen together), then I'm able 
to add other islands even if the old ones are not drawed on screen anymore.

Really strange!
Am I missing something or what?
(QGIS 1.0.0 preview 1 on Windows XP, but also 0.11 acts the same)

Any suggestion?

Thanks
Vito
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PS: The underlying problem is that I'm trying to export this shapefile from 
PostGIS, including even rows without geometry; AFAIK this cannot be done, so 
I put a fake geometry (in a fixed, known position) when exporting a row 
having a null geometry.
Then someone else should edit this shapefile using QGIS and add an island to 
such row to draw the real geometry it should have.
Finally, when importing the shapefile in PostGIS again, the fake geometry will 
be removed.