[REGRESSION][BUG] Color information is lost on frozen assemblies exported to step

[ToniTen]

Related but different to #1180 and #1185 introduced after/as part of the fixes for those issues

Bug Description

When exporting a frozen assembly as a STEP file, color information is lost. Color information is not lost if the assembly to be exported is not frozen, even if some of the parts of the assembly as themselves frozen assemblies

Steps to reproduce

1. Download this archive and unzip it
2. Open color_test.FCStd, should look like this
   
3. Export the assembly (that is not yet frozen) as a STEP file, and open it. It should look like this
   
4. Freeze the assembly, export it as STEP, and open it, it will look like this
   

As you saw at step 3, even if some of the parts were frozen assemblies, color information was preserved as long as the assembly to export was not frozen. Once the assembly to export was frozen, all color information was lost.

This was tested on the latest Snap, without installing Assembly3 manually via the addon manager

FreeCAD version information

OS: Ubuntu Core 20 (XFCE/xubuntu)
Word size of FreeCAD: 64-bit
Version: 2022.407.14555 (Git shallow)
Build type: Release
Branch: (HEAD detached at 2022.04.07-edge)
Hash: 9610830a8fd492b3b3d96f8328507c80f1437cda
Python version: 3.8.10
Qt version: 5.15.3
Coin version: 4.0.1
OCC version: 7.6.1
Locale: Spanish/Spain (es_ES)

[realthunder]

The problem is fixed with the above commit. During testing I've discovered another OCC bug (see realthunder/FreeCAD#310) which has no workaround for the moment. It is not a serious problem as it only happens in very limited cases, one of which is your test file.