Fixed a bug in canvas.types.astro.Compass
Fixed a bug in canvas.types.astro.Compass

When ginga.util.wcsmod.AstropyWCS.radectopix returns nan (caused
by some kind of faulty FITS file), Compass.draw throws an error
that causes the viewer at the top of the Info tab to stop working
properly. I fixed it with a try/except.

stscieisenhamer/ginga,pllim/ginga,naojsoft/ginga,ejeschke/ginga,ejeschke/ginga,pllim/ginga,stscieisenhamer/ginga,naojsoft/ginga,naojsoft/ginga,ejeschke/ginga,stscieisenhamer/ginga,pllim/ginga