deserialization failed: invalid type: null, expected struct RoomSummary

[kevincox]

Client::sync fails with:

Error: deserialization failed: invalid type: null, expected struct RoomSummary at line 1 column 1308

Stack backtrace:
   0: anyhow::error::<impl core::convert::From<E> for anyhow::Error>::from
   1: myapp::main::{{closure}}.17214
   2: myapp::main
   3: std::sys::backtrace::__rust_begin_short_backtrace
   4: main
   5: __libc_start_call_main
   6: __libc_start_main_alias_2
   7: _start

Cargo.lock

[jplatte]

Which homeserver implementation / version?