vty/osmo_counter: use name if description is NULL

`show stats` shows (null) for osmocom_counters when
description is null.

OpenBSC> show  stats
Ungrouped counters:
 (null):        4

Change-Id: I553b88a6fca688924b1f2b49e8cb17e90f057bb1
diff --git a/src/vty/utils.c b/src/vty/utils.c
index 3a0f138..27c1a85 100644
--- a/src/vty/utils.c
+++ b/src/vty/utils.c
@@ -159,9 +159,13 @@
 {
 	struct vty_out_context *vctx = vctx_;
 	struct vty *vty = vctx->vty;
+	const char *description = counter->description;
+
+	if (!counter->description)
+		description = counter->name;
 
 	vty_out(vty, " %s%s: %8lu%s",
-		vctx->prefix, counter->description,
+		vctx->prefix, description,
 		osmo_counter_get(counter), VTY_NEWLINE);
 
 	return 0;