Residual Polygons

Hi,

I am attempting to use JOSM and so far I have been using it successfully. I am using it in conjunction with SUMO. However not so long ago I found a problem which has gotten me stuck. So help would be greatly appreciated!

I downloaded a map from OSM, left it as it is, used polyconvert (from SUMO), and it worked out fine.

Then I spent some time simplifying the map using JOSM. (Deleting and modifying some of the nodes and polygons which I found to be unnecessary for my project.) After doing so, I tried using polyconvert once again, and the following error popped up:

'Error: Polygon "(With polygon number)" has no shape.'

At first I thought that there were some extra polygons not specified in my file, so I intentionally left a single node in the file and tried using polyconvert again. And the same error arises!

Now for me, it is impossible to remove all the work I have done on the map and start over, as I spent many hours modifying it. Therefore the way I see it, there are two solutions (which I do not know how to do!).

1) Copy the deleted polygons from the original file.

2) Remove any possible residuals of the polygons which I deleted.

Obviously I prefer solution (2) but I do not know how to do it..any help would be immensely appreciated! Thanks!