abort trying to dissect ldap controls if the header doesnt look right.

it will not solve the problem in the c06-  testmenageri capture that
contains unknown types of ldap commands   but it will at least 
stop the ldap controls dissector from dumping core.

someone interested in ldap might want to look at those "unknown ldap packets"
in the trace.



svn path=/trunk/; revision=12773

epan/dissectors/packet-ldap.c

@@ -1952,6 +1952,7 @@ static void dissect_ldap_controls(ASN1_SCK *a, proto_tree *tree)
     proto_tree_add_text(tree, a->tvb, a->offset, 0,
                         "ERROR: Couldn't parse LDAP Controls: %s",
                         asn1_err_to_str(ASN1_ERR_WRONG_TYPE));
+    return;
   }
 
   ctrls_item = proto_tree_add_text(tree, a->tvb, start, length, "LDAP Controls");