Unable to change grid size and snap angle

Hello,

I was quite distressed because I couldn't change the grid size and snap 
angle in my document. The toolbar only displayed "16pt" and "45 deg" and 
nothing else was available.

I finally understood that the problem happened because my document was 
converted from an old Ipe6 PDF file with ipeextract / ipe6upgrade. The 
resulting IPE file did not have any <gridsize> nor <anglesize> definitions.

A solution was to copy-paste the drawing from the "bad" document window 
to a blank Ipe window and save as a new file. The resulting document 
could be used satisfactorily.

I write this in case other people would have the same problem and look 
for a solution.

Maybe ipe6upgrade could be improved so as to add defaults for <gridsize> 
and <anglesize>.

Best regards,

O.C.