Fix #144592: FBX exporter: Invalid memory access when exporting tangents.

Since the tangent attributes are now recomputed inside the loop over uv
layers, looping directly over this mesh data is dangerous, as computing
the tangents attributes might trigger some re-allocations, leading to
invalid memory accesses when accessing the next uv layer.

Solved by caching uv layers' names in a list beforehand, the uvlayers
themselves are not even needed for tangent data handling.

Regression from e0a9e98cbd.

scripts/addons_core/io_scene_fbx/export_fbx_bin.py

@@ -1247,8 +1247,11 @@ def fbx_data_mesh_elements(root, me_obj, scene_data, done_meshes):
                     num_loops = len(me.loops)
                     t_ln = np.empty(num_loops * 3, dtype=normal_bl_dtype)
                     # t_lnw = np.zeros(len(me.loops), dtype=np.float64)
-                    for idx, uvlayer in enumerate(me.uv_layers):
-                        name = uvlayer.name
+                    # WARNING: Since tangent layers are recomputed inside the loop, do not directly iterate over the
+                    # uvlayers. Instead, cache their keys (names), and use this cached data inside the loop to compute
+                    # the tangent layers.
+                    uvlayer_names = [uvl.name for uvl in me.uv_layers]
+                    for idx, name in enumerate(uvlayer_names):
                         # Annoying, `me.calc_tangent` errors in case there is no geometry...
                         if num_loops > 0:
                             me.calc_tangents(uvmap=name)