[GRASS5] [bug #2084] (grass) i.rectify never finishes processing with null data in region

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this bug's URL: http://intevation.de/rt/webrt?serial_num=2084
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Subject: i.rectify never finishes processing with null data in region

Platform: GNU/Linux/i386
grass obtained from: Mirror of Trento site
grass binary for platform: Compiled from Sources
GRASS Version: 5.0.2

I was using a USGS DRG on a 7.5 Quad.
I had another map that would be a small part of that.
I was going to rectify the map and overlay it on the topo.
I found that I needed to make null the parts of the small map that were blank 
so that I could overlay the topo map and not lose data by overwriting with blanks.  I was able to rectify the file and then remove the blank areas while using rectified destination location.  This rectification would take about 1 1/2 hours.
This was not quite right so I decided to change the blank raster data to nulls before rectification.  When I then rectified the file, the job never finished.
After about 24 hours I cancelled the job.  I was only using 3 GCPs and was doing a linear transformation (1 dim).  I only had one geo-referenced coordinate, but I had the scale and the north south direction on the scanned map which I used to calculate 2 more GCPs.  As I write this I wonder what would happen if one of my GCPs, was made null.  Would it mess up the rectification?

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