Occasional panic in crypto_mbedtls.rs

[mibes]

During pairing with Apple Home a panic was triggered in crypto_mbedtls.rs. This happened only once and I was unable to reproduce the issue so far. Will update this issue if it happens again.

[2023-01-15T10:52:02Z INFO  matter::data_model::sdm::noc] Handling Command CSRRequest
[2023-01-15T10:52:02Z INFO  matter::data_model::sdm::noc] Received CSR Nonce:OctetStr([52, 226, 46, 191, 82, 255, 246, 250, 115, 248, 188, 209, 33, 137, 211, 219, 31, 19, 195, 59, 234, 232, 71, 18, 40, 161, 131, 213, 218, 57, 218, 134])
thread 'main' panicked at 'attempt to subtract with overflow', src/crypto/crypto_mbedtls.rs:290:19
note: run with `RUST_BACKTRACE=1` environment variable to display a backtrace