RT2560: missing NULL check in ocsp_req_find_signer

If we don't find a signer in the internal list, then fall
through and look at the internal list; don't just return NULL.

Reviewed-by: Dr. Stephen Henson <steve@openssl.org>
diff --git a/crypto/ocsp/ocsp_vfy.c b/crypto/ocsp/ocsp_vfy.c
index 2767183..fc0d4cc 100644
--- a/crypto/ocsp/ocsp_vfy.c
+++ b/crypto/ocsp/ocsp_vfy.c
@@ -436,8 +436,11 @@
 	if(!(flags & OCSP_NOINTERN))
 		{
 		signer = X509_find_by_subject(req->optionalSignature->certs, nm);
-		*psigner = signer;
-		return 1;
+		if (signer)
+			{
+			*psigner = signer;
+			return 1;
+			}
 		}
 
 	signer = X509_find_by_subject(certs, nm);