gen_key example Segmentation fault when called without arguments

[PiotrBzdrega]

Summary

A problem occurs when entropy is going to be free, but the memory was not allocated beforehand.

mbedtls_entropy_free(&entropy);

below expression can be called before recognition of number of arguments to fix it.

mbedtls_entropy_init(&entropy);

System information

Mbed TLS version (number or commit id): development commit: c3d17cd
Operating system and version: Windows10 22H2 (Build 19045.3930) & Ubuntu 22.04.3 LTS

Steps to reproduce

[Linux]
:/home/git/embd/build/programs/pkey$ ./gen_key

 usage: gen_key param=<>...

 acceptable parameters:
    type=rsa|ec           default: rsa
    rsa_keysize=%d        default: 4096
    ec_curve=%s           see below
    filename=%s           default: keyfile.key
    format=pem|der        default: pem
    use_dev_random=0|1    default: 0

 available ec_curve values:
    secp521r1 (default)
    brainpoolP512r1
    secp384r1
    brainpoolP384r1
    secp256r1
    secp256k1
    brainpoolP256r1
    secp224r1
    secp224k1
    secp192r1
    secp192k1
    x25519
    x448
 - ERROR - Generic error
Segmentation fault

Additional information

[Windows]