Do not output anything when there is no valid decryption key.

When the decryption fails due to missing decryption key it is better
to not output anything. Before this patch in case of missing decryption
key the PSI tables were still being written to the output and this
could confuse some monitoring systems to think that the stream is
working.

process.c

@@ -244,6 +244,8 @@ void *decode_thread(void *_ts) {
 static inline void output_write(struct ts *ts, uint8_t *data, unsigned int data_size) {
 	if (!data)
 		return;
+	if (!ts->camd.key->is_valid_cw)
+		return;
 	if (!ts->rtp_output) {
 		write(ts->output.fd, data, data_size);
 	} else {