bugfix: handling possible nullptr access.

update: replace clear be resize( 0 ) at some places to avoid double allocations ( only a micro optimization ).

Signed-off-by: Kim Kulling <kim.kulling@googlemail.com>

code/DeboneProcess.cpp

@@ -111,7 +111,7 @@ void DeboneProcess::Execute( aiScene* pScene)
 
 	if(numSplits)	{
 		// we need to do something. Let's go.
-		mSubMeshIndices.clear();
+		//mSubMeshIndices.clear(); really needed?
 		mSubMeshIndices.resize(pScene->mNumMeshes);
 
 		// build a new array of meshes for the scene