fdtgrep: Deal with NULL data passed to check_type_include()

Since the parameter can be NULL we must be careful not to dereference it
in this case.

Signed-off-by: Simon Glass <sjg@chromium.org>
Reported-by: Coverity (CID: 163250)
Fixes: 1043d0a0 (fdt: Add fdtgrep tool)
1 file changed