Examples failing

[EDGDrummond]

After cloning the repo and running the examples as per the instructions in the readme files, we have these issues:

1. When running RUST_BACKTRACE=1 cargo run --release --example halo2_example

we get this error

thread 'main' panicked at rcc-halo2/src/plaf.rs:39:44:
Cannot convert to toml: Error { inner: UnsupportedNone }
stack backtrace:
   0: rust_begin_unwind
             at /rustc/cc66ad468955717ab92600c770da8c1601a4ff33/library/std/src/panicking.rs:595:5
   1: core::panicking::panic_fmt
             at /rustc/cc66ad468955717ab92600c770da8c1601a4ff33/library/core/src/panicking.rs:67:14
   2: core::result::unwrap_failed
             at /rustc/cc66ad468955717ab92600c770da8c1601a4ff33/library/core/src/result.rs:1652:5
   3: rcc_halo2::plaf::serialize
   4: rcc_halo2::builder::H2Builder::write_config
   5: rcc_halo2::builder::H2Builder::compile_from_commandline
   6: halo2_example::main

2. After running time cargo run --release --example mock_example and then running time cargo run --release --example mock_example_runtime 999 we get this error

error: casting `&T` to `&mut T` is undefined behavior, even if the reference is unused, consider instead using an `UnsafeCell`
  --> circuit-examples/examples/mock_example_runtime_lib.rs:11:18
   |
11 |         unsafe { &mut *(wires.get_unchecked(id) as *const WireVal as *mut WireVal) }
   |                  ^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^
   |
   = note: `#[deny(invalid_reference_casting)]` on by default