[PATCH] USB: UEAGLE : null pointer dereference fix

this patch fix potential null pointer dereference.  Found by the
Coverity checker.

Signed-off-by: Duncan Sands <baldrick@free.fr>
Signed-off-by: Matthieu CASTET <castet.matthieu@free.fr>
Signed-off-by: Greg Kroah-Hartman <gregkh@suse.de>