The pending_value_handle needs to be freed and reset before calling
mp_bluetooth_gattc_on_read_write_status(), which will call the Python IRQ
handler, which may in turn call back into BTstack to perform an action like
a write. In that case the pending_value_handle will need to be available
for the write/read/etc to proceed.
Fixes issue #13611.
Signed-off-by: Damien George <damien@micropython.org>
b4f59984f7