Callsigns 6 characters long where not being null terminated

main.c

@@ -55,7 +55,7 @@ int main(int argc, char *argv[])
 		case 'c':
 			if(strlen(optarg) > 6)
 				fprintf(stderr, "Warning: callsign is longer than 6 characters.\n");
-			strncpy(callsign, optarg, 6);
+			strncpy(callsign, optarg, 7);
 			break;
 		case 'i': image_id = atoi(optarg); break;
 		case 't': droptest = atoi(optarg); break;