modules: hostap: supp_api: Fix possible null deference

Ensure 'params' is not NULL before accessing its fields.

Prevents possible null pointer dereference when calling
strlen(params->ssid).

Delay access to ssid->ssid and ssid->ssid_len until after null check.

Prevents potential crash if wpa_s->current_ssid is NULL.

Signed-off-by: Gaetan Perrot <gaetan.perrot@spacecubics.com>