I guess this code is supposed to take a NUL character, but if we write
zero bytes then it tries to write -1 characters and crashes.
Fixes: c91b865cb14d ("iwlwifi: mvm: support description for user triggered fw dbg collection") Signed-off-by: Dan Carpenter <dan.carpenter@oracle.com> Signed-off-by: Luca Coelho <luciano.coelho@intel.com>