ASCI: Fix length indicator in template tr_BSSMAP_IE_GroupCallRef

Any length must match, not just 0.

Related: OS#4854
Change-Id: I34546609a80f714438abe985697dabc846c89701
diff --git a/library/BSSMAP_Templates.ttcn b/library/BSSMAP_Templates.ttcn
index 89efeb8..03479c1 100644
--- a/library/BSSMAP_Templates.ttcn
+++ b/library/BSSMAP_Templates.ttcn
@@ -2100,7 +2100,7 @@
 template (present) BSSMAP_IE_GroupCallReference
 tr_BSSMAP_IE_GroupCallRef(template (present) GroupCallRef group_call_ref) :={
 	elementIdentifier := '37'O,
-	lengthIndicator := 0, // overwritten
+	lengthIndicator := ?,
 	descrGroupbroadcastCallRef := group_call_ref
 }