ios 0.20.16: crash when assembling the mesh with texture

[matlabbe]

#0	(null) in pcl::TextureMapping<pcl::PointXYZ>::textureMeshwithMultipleCameras2(pcl::TextureMesh&, std::__1::vector<pcl::texture_mapping::Camera, Eigen::aligned_allocator<pcl::texture_mapping::Camera> > const&... ()
#1	(null) in pcl::TextureMapping<pcl::PointXYZ>::textureMeshwithMultipleCameras2(pcl::TextureMesh&, std::__1::vector<pcl::texture_mapping::Camera, Eigen::aligned_allocator<pcl::texture_mapping::Camera> > const&... ()
#2	(null) in rtabmap::util3d::createTextureMesh(std::__1::shared_ptr<pcl::PolygonMesh> const&, std::__1::map<int, rtabmap::Transform, std::__1::less<int>, std::__1::allocator<std::__1::pair<int const, rtabmap::... ()
#3	(null) in rtabmap::util3d::createTextureMesh(std::__1::shared_ptr<pcl::PolygonMesh> const&, std::__1::map<int, rtabmap::Transform, std::__1::less<int>, std::__1::allocator<std::__1::pair<int const, rtabmap::... ()
#4	0x0000000102878fc4 in 0x102830000 at /Users/mathieu/workspace/rtabmap/app/android/jni/RTABMapApp.cpp:2877
#5	0x0000000102853924 in exportMeshNative at /Users/mathieu/workspace/rtabmap/app/ios/RTABMapApp/NativeWrapper.cpp:144
#6	0x00000001028c91a0 in 0x102830000 at /Users/mathieu/workspace/rtabmap/app/ios/RTABMapApp/RTABMap.swift:158
#7	0x00000001028c3d40 in partial apply for closure #1 in closure #2 in ViewController.export(isOBJ:meshing:regenerateCloud:optimized:optimizedMaxPolygons:previousState:) at /Users/mathieu/workspace/rtabmap/app/ios/RTABMapApp/ViewController.swift:1581
#8	0x00000001028bc9c4 in closure #1 in static OS_dispatch_queue.background(delay:background:completion:) at /Users/mathieu/workspace/rtabmap/app/ios/RTABMapApp/ViewController.swift:2220
#9	(null) in thunk for @escaping @callee_guaranteed () -> () ()

This issue has been detected in 0.20.16, but would be already present in older releases.

Need more testing to debug this. Things to do to reproduce the bug and keep enough data to debug:

1. New Scan from default settings of version 0.20.16 (in the crash above, it happened with a scan over 4 rooms of size)
2. Save the map before doing the assembling (click Save First after a scan)
3. Note the Memory Usage
4. Click on Optimize... -> Standard Optimization
5. Click on Assemble... -> Optimized mesh... -> Textured Mesh

Repeat until it crashes in step 5, then share database.