isdn: guard against a potential NULL pointer dereference in old_capi_manufacturer()

isdn: guard against a potential NULL pointer dereference in old_capi_manufacturer()

In drivers/isdn/capi/kcapi.c::old_capi_manufacturer(), if the call to
get_capi_ctr_by_nr(ldef.contr); in line 823 returns NULL, then we'll be
dereferencing a NULL pointer in the very next line.

(Found by Coverity checker as bug #402)

Signed-off-by: Jesper Juhl <[email protected]>
Acked-by: Karsten Keil <[email protected]>
Signed-off-by: Andrew Morton <[email protected]>
Signed-off-by: Linus Torvalds <[email protected]>