[Fdo_issues] SDF: fixed defect (SDF crash when selecting class without primary geometry)

[Dan Stoica]

Fixed an unhandled NULL pointer case (i.e. NULL returned by
GetGeometryExtents() because of multiple geometries and lack of 'main
geometry' setting). 

Changed files:
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\branches\3.2.x\Providers\SDF\Src\Provider\SdfQueryOptimizer.cpp