CDRIVER-3539 adds null checks

Adds null checks after calls to _mongoc_cluster_create_server_stream.

Author: Andrew Witten

src/libmongoc/src/mongoc/mongoc-cluster-cyrus.c

@@ -84,6 +84,11 @@ _mongoc_cluster_auth_node_cyrus (mongoc_cluster_t *cluster,
       server_stream = _mongoc_cluster_create_server_stream (
          cluster->client->topology, sd->id, stream, error);
 
+      if (!server_stream) {
+         bson_destroy (&cmd);
+         goto failure;
+      }
+
       if (!mongoc_cmd_parts_assemble (&parts, server_stream, error)) {
          mongoc_server_stream_cleanup (server_stream);
          bson_destroy (&cmd);

src/libmongoc/src/mongoc/mongoc-cluster.c

@@ -1062,6 +1062,11 @@ _mongoc_cluster_auth_node_cr (mongoc_cluster_t *cluster,
    parts.prohibit_lsid = true;
    server_stream = _mongoc_cluster_create_server_stream (
       cluster->client->topology, sd->id, stream, error);
+   if (!server_stream) {
+      bson_destroy (&command);
+      bson_destroy (&reply);
+      RETURN (false);
+   }
 
    if (!mongoc_cluster_run_command_parts (
           cluster, server_stream, &parts, &reply, error)) {
@@ -1191,6 +1196,12 @@ _mongoc_cluster_auth_node_plain (mongoc_cluster_t *cluster,
    parts.prohibit_lsid = true;
    server_stream = _mongoc_cluster_create_server_stream (
       cluster->client->topology, sd->id, stream, error);
+   if (!server_stream) {
+      bson_destroy (&b);
+      bson_destroy (&reply);
+      return false;
+   }
+
    ret = mongoc_cluster_run_command_parts (
       cluster, server_stream, &parts, &reply, error);
    mongoc_server_stream_cleanup (server_stream);
@@ -1299,6 +1310,12 @@ _mongoc_cluster_auth_node_x509 (mongoc_cluster_t *cluster,
    parts.prohibit_lsid = true;
    server_stream = _mongoc_cluster_create_server_stream (
       cluster->client->topology, sd->id, stream, error);
+   if (!server_stream) {
+      bson_destroy (&cmd);
+      bson_destroy (&reply);
+      return false;
+   }
+
    ret = mongoc_cluster_run_command_parts (
       cluster, server_stream, &parts, &reply, error);
    mongoc_server_stream_cleanup (server_stream);
@@ -1429,7 +1446,11 @@ _mongoc_cluster_run_scram_command (mongoc_cluster_t *cluster,
    parts.prohibit_lsid = true;
    server_stream = _mongoc_cluster_create_server_stream (
       cluster->client->topology, server_id, stream, error);
-   BSON_ASSERT (server_stream);
+   if (!server_stream) {
+      bson_destroy (reply);
+      return false;
+   }
+
    if (!mongoc_cluster_run_command_parts (
           cluster, server_stream, &parts, reply, error)) {
       mongoc_server_stream_cleanup (server_stream);
@@ -3021,6 +3042,10 @@ mongoc_cluster_check_interval (mongoc_cluster_t *cluster, uint32_t server_id)
       parts.prohibit_lsid = true;
       server_stream = _mongoc_cluster_create_server_stream (
          cluster->client->topology, server_id, stream, &error);
+      if (!server_stream) {
+         bson_destroy (&command);
+         return false;
+      }
       r = mongoc_cluster_run_command_parts (
          cluster, server_stream, &parts, NULL, &error);