[2387] Add some assertions anyway

src/lib/dns/rdata/generic/detail/nsec_bitmap.cc

@@ -96,6 +96,7 @@ buildBitmapsFromLexer(const char* const rrtype_name,
         }
 
         // token is now assured to be of type STRING.
+        assert(token.getType() == MasterToken::STRING);
 
         have_rrtypes = true;
         token.getString(type_str);

src/lib/dns/rdata/generic/dnskey_48.cc

@@ -173,6 +173,7 @@ DNSKEY::constructFromLexer(MasterLexer& lexer) {
         }
 
         // token is now assured to be of type STRING.
+        assert(token.getType() == MasterToken::STRING);
 
         token.getString(keydata_substr);
         keydata_str.append(keydata_substr);