Area feature labeling code does not check for NaN values from centroid computation

[waltweltonlair]

The new stylization code which computes labels for polygon features calls a method which computes the centroid of each feature. In some cases this method fails (when it can't find a good centroid which falls inside the polygon feature's bounds), and it then returns NaN values for the centroid coordinates. The labeling code, however, doesn't check for this condition.

[waltweltonlair]

Fixed in the trunk stream with submission  https://trac.osgeo.org/mapguide/changeset/3167.

[waltweltonlair]

Fixed in the branch stream with submission  https://trac.osgeo.org/mapguide/changeset/3168.