static code analyzer complain:

hw/usb/dev-smartcard-reader.c:816:5: warning: Null pointer passed as an argument to a 'nonnull' parameter
    memcpy(p->abData, data, len);
    ^~~~~~~~~~~~~~~~~~~~~~~~~~~~

Reported-by: Clang Static Analyzer
Signed-off-by: NPhilippe Mathieu-Daudé <f4bug@amsat.org>
Signed-off-by: NMichael Tokarev <mjt@tls.msk.ru>