PreparedGeometryFactory crashes if called with null pointer

[mloskot]

Current version of PreparedGeometryFactory​ crashes (both create() and prepare() calls) if called with null pointer to Geometry type.

Geometry* p = PreparedGeometryFactory::prepare(0);
// segmentation fault here

It should throw an exception or return null pointer, instead of crashing.

[cthibert]

This fix will check for a null geometry and throw an exception if it is. Test cases were updated as well.

[mloskot]

Thanks for the patch!

Fixed in trunk (r2187)