ColladaExporter: remove self assignment.

code/ColladaExporter.cpp

@@ -691,7 +691,6 @@ void ColladaExporter::WriteMaterials()
 
     materials[a].shininess.exist = mat->Get( AI_MATKEY_SHININESS, materials[a].shininess.value) == aiReturn_SUCCESS;
     materials[a].transparency.exist = mat->Get( AI_MATKEY_OPACITY, materials[a].transparency.value) == aiReturn_SUCCESS;
-    materials[a].transparency.value = materials[a].transparency.value;
     materials[a].index_refraction.exist = mat->Get( AI_MATKEY_REFRACTI, materials[a].index_refraction.value) == aiReturn_SUCCESS;
   }