fix grp seq copy

src/rds.c

@@ -619,7 +619,7 @@ void set_rds_cg(uint16_t* blocks) {
 
 void set_rds_grpseq(unsigned char* grpseq) {
 	uint8_t len = 0;
-	memset(rds_data.grp_sqc, ' ', 24);
+	memset(rds_data.grp_sqc, 0, 24);
 	while (*grpseq != 0 && len < 24)
 		rds_data.grp_sqc[len++] = *grpseq++;
 }