bpftool: fix potential NULL pointer dereferencing in prog_dump()

bpftool: fix potential NULL pointer dereferencing in prog_dump()

A NULL pointer dereference could occur if ksyms
is not properly checked before usage in the prog_dump() function.

Fixes: b053b439b72a ("bpf: libbpf: bpftool: Print bpf_line_info during prog dump")
Signed-off-by: Amir Mohammadi <amiremohamadi@yahoo.com>
Reviewed-by: Quentin Monnet <qmo@kernel.org>
Acked-by: John Fastabend <john.fastabend@gmail.com>
Link: https://lore.kernel.org/r/20241121083413.7214-1-amiremohamadi@yahoo.com
Signed-off-by: Alexei Starovoitov <ast@kernel.org>