BF-44437 encounters an issue where ref->page == NULL and we are trying to read or reconstruct a modify when the full base value is unavailable. This suggests that  __wt_modify_reconstruct_from_upd_list() failing to find a full update in the update chain and falling back to the on-page value via the upd == NULL path, but with the original page is missing.

The crash came from a resmoke run of jstests/core/query/query_settings/query_settings_size_limits.js on a disaggregated replset.

To debug the issue, we can add extra diagnostic information in that spot that would call __wt_value_return_buf with the missing page, and check if cbt->ref == NULL || cbt->ref->page == NULL and, if so: log the full state and abort here, instead of downstream __wt_value_return_buf deref.