asn1_der_decoding2: fix flag checking

Signed-off-by: Nikos Mavrogiannopoulos <nmav@gnutls.org>
diff --git a/lib/decoding.c b/lib/decoding.c
index d57aa93..8366d48 100644
--- a/lib/decoding.c
+++ b/lib/decoding.c
@@ -1177,7 +1177,7 @@
 	        }
 
               ptag = der + counter - inner_tag_len;
-              if (flags & ASN1_DECODE_FLAG_STRICT_DER || !(ptag[0] & ASN1_CLASS_STRUCTURED))
+              if ((flags & ASN1_DECODE_FLAG_STRICT_DER) || !(ptag[0] & ASN1_CLASS_STRUCTURED))
                 {
 	          len2 =
 		    asn1_get_length_der (der + counter, ider_len, &len3);