Fix no-comp

Commit 88393244 removed some NULL checks from the stack code. This caused
a no-comp build to fail in the client and server fuzzers.
Reviewed-by: NRichard Levitte <levitte@openssl.org>
(Merged from https://github.com/openssl/openssl/pull/6893)

fuzz/client.c

@@ -49,8 +49,8 @@ int FuzzerInitialize(int *argc, char ***argv)
     idx = SSL_get_ex_data_X509_STORE_CTX_idx();
     FuzzerSetRand();
     comp_methods = SSL_COMP_get_compression_methods();
-    sk_SSL_COMP_sort(comp_methods);
-
+    if (comp_methods != NULL)
+        sk_SSL_COMP_sort(comp_methods);
 
     return 1;
 }

fuzz/server.c

@@ -496,8 +496,8 @@ int FuzzerInitialize(int *argc, char ***argv)
     idx = SSL_get_ex_data_X509_STORE_CTX_idx();
     FuzzerSetRand();
     comp_methods = SSL_COMP_get_compression_methods();
-    sk_SSL_COMP_sort(comp_methods);
-
+    if (comp_methods != NULL)
+        sk_SSL_COMP_sort(comp_methods);
 
     return 1;
 }