Blind attempt to fix T45931: Blender Fails to generate previews.

Cannot reproduce the issue here on linux, but have the feeling windows builds are much
more easily broken with referencing bad data from bpy. So here guessing direct loop
over bpy.data.xxx when you do add and remove stuff from said xxx inside the loop
is not a good idea - which seems logical in the end. :P

1 files changed, 21 insertions, 14 deletions

diff --git a/release/scripts/modules/bl_previews_utils/bl_previews_render.py b/release/scripts/modules/bl_previews_utils/bl_previews_render.py
index 0ef49601c43..e9c6270a177 100644
--- a/release/scripts/modules/bl_previews_utils/bl_previews_render.py
+++ b/release/scripts/modules/bl_previews_utils/bl_previews_render.py
@@ -320,14 +320,17 @@ def do_previews(do_objects, do_groups, do_scenes, do_data_intern):
     prev_scenename = bpy.context.screen.scene.name
 
     if do_objects:
-        prev_shown = tuple(ob.hide_render for ob in bpy.data.objects)
-        for ob in bpy.data.objects:
+        data_objects_names = tuple(ob.name for ob in bpy.data.objects)
+        prev_shown = tuple(bpy.data.objects[obname].hide_render for obname in data_objects_names)
+        for obname in data_objects_names:
+            ob = bpy.data.objects[obname]
             if ob in objects_ignored:
                 continue
             ob.hide_render = True
-        for root in bpy.data.objects:
-            if root.name in objects_ignored:
+        for root_name in data_objects_names:
+            if root_name in objects_ignored:
                 continue
+            root = bpy.data.objects[root_name]
             if root.type not in OBJECT_TYPES_RENDER:
                 continue
             objects = (root.name,)
@@ -366,13 +369,15 @@ def do_previews(do_objects, do_groups, do_scenes, do_data_intern):
                 scene.objects.unlink(ob)
                 ob.hide_render = True
 
-        for ob, is_rendered in zip(bpy.data.objects, prev_shown):
-            ob.hide_render = is_rendered
+        for obname, is_rendered in zip(data_objects_names, prev_shown):
+            bpy.data.objects[obname].hide_render = is_rendered
 
     if do_groups:
-        for grp in bpy.data.groups:
-            if grp.name in groups_ignored:
+        data_groups_names = tuple(grp.name for grp in bpy.data.groups)
+        for grpname in data_groups_names:
+            if grpname in groups_ignored:
                 continue
+            grp = bpy.data.groups[grpname]
             objects = tuple(ob.name for ob in grp.objects)
 
             render_engine = objects_render_engine_guess(objects)
@@ -400,19 +405,21 @@ def do_previews(do_objects, do_groups, do_scenes, do_data_intern):
             do_save = False  # Do not save file if something went wrong here, we could 'pollute' it with temp data...
 
     if do_scenes:
-        for scene in bpy.data.scenes:
-            has_camera = scene.camera is not None
-            bpy.context.screen.scene = scene
+        data_scenes_names = tuple(sce.name for sce in bpy.data.scenes)
+        for scename in data_scenes_names:
+            sce = bpy.data.scenes[scename]
+            has_camera = sce.camera is not None
+            bpy.context.screen.scene = sce
             render_context = render_context_create('__SCENE', objects_ignored)
-            scene.update()
+            sce.update()
 
             objects = None
             if not has_camera:
                 # We had to add a temp camera, now we need to place it to see interesting objects!
-                objects = tuple(ob.name for ob in scene.objects
+                objects = tuple(ob.name for ob in sce.objects
                                         if (not ob.hide_render) and (ob.type in OBJECT_TYPES_RENDER))
 
-            preview_render_do(render_context, 'scenes', scene.name, objects)
+            preview_render_do(render_context, 'scenes', sce.name, objects)
 
             if not render_context_delete(render_context):
                 do_save = False