An RCF message containing a timeout results in a NULL-ptr dereference if
no RRQ has been seen before.

Noticed by the "SATURN tool", reported by Thomas Dillig <tdillig@stanford.edu>
and Isil Dillig <isil@stanford.edu>.
Signed-off-by: Patrick McHardy <kaber@trash.net>
Signed-off-by: David S. Miller <davem@davemloft.net>