Fix #126942: Memory Leak when creating Pose Asset without camera

In this case, the `PoseBackup` created by
`action_preview_render_prepare` wasnt cleaned up properly (because
`action_preview_render` was earlied out).

So to resolve, call `action_preview_render_cleanup` as well when
earlying out)

Pull Request: https://projects.blender.org/blender/blender/pulls/127067

source/blender/editors/render/render_preview.cc

@@ -1005,6 +1005,7 @@ static void action_preview_render(IconPreview *preview, IconPreviewSize *preview
   if (camera_eval == nullptr) {
     printf("Scene has no camera, unable to render preview of %s without it.\n",
            preview->id->name + 2);
+    action_preview_render_cleanup(preview, pose_backup);
     return;
   }