Fixed endless loop in the eclipse finder. Bodies with intersecting bounding spheres

were considered to be in eclipse. If they happened to be fixed relative to each other,
the loop to find the eclipse duration would never terminate. An extra line of code
was added to reject eclipses between intersecting bodies.

src/celestia/eclipsefinder.cpp

@@ -92,7 +92,10 @@ bool EclipseFinder::testEclipse(const Body& receiver, const Body& caster,
                                Ray3d(posCaster, posCaster - Point3d(0, 0, 0)));
         if (dist < R)
         {
-            return true;
+            // Ignore "eclipses" where the caster and receiver have
+            // intersecting bounding spheres.
+            if (distToCaster > caster.getRadius())
+                return true;
         }
     }