CID-102166 (Coverity) guard against out-of-bounds read

Author: rcsanchez97

src/libmongoc/tests/mock_server/request.c

@@ -1097,6 +1097,7 @@ request_from_op_msg (request_t *request, const mongoc_rpc_t *rpc)
    bson_iter_t iter;
    bson_string_t *msg_as_str = bson_string_new ("OP_MSG");
 
+   BSON_ASSERT (rpc->msg.n_sections <= 2);
    for (section_no = 0; section_no < rpc->msg.n_sections; section_no++) {
       bson_string_append (msg_as_str, (section_no > 0 ? ", " : " "));
       section = &rpc->msg.sections[section_no];