preproc: Fix sigsegv in find_cc
preproc: Fix sigsegv in find_cc

For specially formed code we can have skip_white_
to end up with nil pointer which should be taken
into account.

https://bugzilla.nasm.us/show_bug.cgi?id=3392435

Signed-off-by: Cyrill Gorcunov <7a1ea01eee6961eb1e372e3508c2670446d086f4@gmail.com>

techkey/nasm,techkey/nasm,techkey/nasm,techkey/nasm,techkey/nasm