The constructor sets `RadioLibInterface::instance = this` immediately,
before `init()` runs. `initLoRa()` in RadioInterface.cpp creates each
radio variant with `new SX1262Interface(...)` or similar, then calls
`init()`, and if init fails the `unique_ptr<RadioInterface>` is reset
to nullptr — destroying the object — while the static `instance`
pointer continues to point at the freed memory.
Main loop then checks `RadioLibInterface::instance != nullptr` and
calls `pollMissedIrqs()` or `resetAGC()` on the dangling pointer →
Guru Meditation (IllegalInstruction / LoadProhibited).
Reported in #9880 on an ESP32-S3 dev board without radio hardware
attached, where init always fails and the leftover pointer crashes
the device on the next `loop()` iteration.
Fix: add a virtual destructor to `RadioLibInterface` that clears the
static pointer iff it still references this object. A later successful
init() may have replaced `instance` with a different interface — the
`instance == this` guard preserves that case.
Fixes#9880
Co-authored-by: Ben Meadors <benmmeadors@gmail.com>