Fix issue caused by NULL at msg pointer

when malloc() failed to allocate memory for msg buffer.
msg buffer can be NULL. Add a NULL check to return
before passing to snprintf() in wpas_auth_failed() api

Bug: 262328781
Test: STA connect/disconnect
Change-Id: Ic3cf55f5c21d2d955fa665a645674a0127f26528
1 file changed