diag: Add protection while accessing usb_info's buffer table

Currently there a possibility of NULL pointer dereference while
accessing usb_info's buffer table due to missing proper protection.
The patch adds protection for the same.

Change-Id: I974a70a48e7ac47b42bc237aac4db1b9e47be6be
Signed-off-by: Hardik Arya <harya@codeaurora.org>
1 file changed