labels.c: Fix NULL dereference on too long identifiers
labels.c: Fix NULL dereference on too long identifiers

In case if label is local and exceed maximum allowed length
we get NULL dereference. Fix it and warn a user about an accident.

Note that we don't print identifier itself since we know it's too
big. Line number of error is enough.

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

projedi/nasm,Distrotech/nasm,Distrotech/nasm,Distrotech/nasm,letolabs/nasm,turingstudio/nasm,techkey/nasm,techkey/nasm,turingstudio/nasm,turingstudio/nasm,turingstudio/nasm,projedi/nasm,techkey/nasm,projedi/nasm,letolabs/nasm,projedi/nasm,letolabs/nasm,Distrotech/nasm,projedi/nasm,techkey/nasm,techkey/nasm