fix broken bone optimization if some verts in a mesh aren't associated with a bone

stepmania/src/RageModelGeometry.cpp

@@ -23,17 +23,14 @@ void RageModelGeometry::OptimizeBones()
     {
 		msMesh& mesh = m_Meshes[i];
 
+		if( mesh.Vertices.empty() )
+			continue;	// nothing to optimize
+
 		// check to see if all vertices have the same bone index
 		bool bAllVertsUseSameBone = true;
 		
-		char nBoneIndex;
-		if( !mesh.Vertices.empty() )
-			nBoneIndex = mesh.Vertices[0].bone;
-		else
-			nBoneIndex = (char)-1;
+		char nBoneIndex	= mesh.Vertices[0].bone;
 
-		if( nBoneIndex != -1 )
-		{
 		for (unsigned j = 1; j < mesh.Vertices.size(); j++)
 		{
 			if( mesh.Vertices[j].bone != nBoneIndex )
@@ -42,7 +39,7 @@ void RageModelGeometry::OptimizeBones()
 				break;
 			}
 		}
-		}
+
 		if( bAllVertsUseSameBone )
 		{
 			mesh.nBoneIndex = nBoneIndex;