Altered exception message for NiTriBasedGeomData::SetTriangles

Casting functions now check for NULL as of last commit.

obj/NiTriBasedGeomData.cpp

@@ -135,5 +135,5 @@ float NiTriBasedGeomData::GetRadius() const {
 }
 
 void NiTriBasedGeomData::SetTriangles( const vector<Triangle> & in ) {
-   throw runtime_error("SetTriangles is a must be implemented in the derived class.");
+   throw runtime_error("SetTriangles is not implemented for this object.");
 }
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