L3_Templates: Fix compiler warning about missing qualifier

L3_Templates.ttcn: In TTCN-3 module `L3_Templates':
 L3_Templates.ttcn:120.1-125.1: In template definition `tr_MI_IMSI':
  L3_Templates.ttcn:122.25-124.2: In template for record field `oddEvenInd_identity':
   L3_Templates.ttcn:123.11-28: In template for union field `imsi':
    L3_Templates.ttcn:123.23-28: In actual parameter list of function `@L3_Templates.f_tr_MI_IMSI':
     L3_Templates.ttcn:123.24-27: In parameter #1 for `digits':
      L3_Templates.ttcn:123.24-27: warning: Inadequate restriction on the referenced template parameter `imsi', this may cause a dynamic test case error at runtime
      L3_Templates.ttcn:120.37-59: note: Referenced template parameter is here

Change-Id: Ia6979dff7d3c58f8609ebe55de2550446c3f1781
diff --git a/library/L3_Templates.ttcn b/library/L3_Templates.ttcn
index f072f78..8c0f494 100644
--- a/library/L3_Templates.ttcn
+++ b/library/L3_Templates.ttcn
@@ -117,7 +117,7 @@
 		return f_enc_IMSI_L3(valueof(digits))
 	}
 }
-template MobileIdentityV tr_MI_IMSI(template hexstring imsi) := {
+template MobileIdentityV tr_MI_IMSI(template (present) hexstring imsi) := {
 	typeOfIdentity := '001'B,
 	oddEvenInd_identity := {
 		imsi := f_tr_MI_IMSI(imsi)