Grid NxN counter on menu bar does not get refreshed

[davidh]

1. create a NxN grid over an image e.g. 5x5
2. create a NxN grid over another image with a different number of squares e.g.7x7
3. make active the first image, its grid is 5x5 but the counter reads 7x7
4. set the grid of the first image from 5x5 to None
3. make active the second image, its grid is 7x7 but the counter reads 5x5

[jsachs]

Fixed for next release.